Search

Purpose: To evaluate the embryological and pregnancy outcomes of women who failed in their first IVF treatment if they attempted a second cycle. Methods: For evaluating the embryological outcomes, the study cohort included 1,227 women who failed to obtain a live birth after the initial IVF cycle from September 2018 to August 2021 and returned for a second attempt. To evaluate reproductive outcomes including live birth rates (LBRs), 1227 women who returned for a second attempt were compared with 13,195 women undergoing their first oocyte retrieval with blastocyst culture attempted during the same study period. Results: In women who had a second cycle, the median number of oocyte retrieved (11 vs 9), fertilized oocytes (7 vs 5), usable embryos (6 vs 4) and blastocysts (3 vs 1) was higher in the second cycle compared to the first cycle (All p < 0.001). Blastocyst formation rates were significantly increased from 33% in the first cycle to 50% in the second cycle across the age group (p < 0.001). However, the primary transfer LBRs were significantly lower in the second cycle than that in the initial cycle (40.82% versus 51.79%, aOR: 0.74 [0.65, 0.84]). LBRs in the second cycle were 42.26%, 42.68%, 25.49% and 16.22% in women aged < 35, 35–37, 38–40, and > 40 years. Conclusion: There was a notable enhancement in laboratory outcomes following the second attempt in women whose initial IVF cycles were unsuccessful. However, the uncertainty inherent in the successful implantation and the consequent progression to live birth remains a significant challenge. [ABSTRACT FROM AUTHOR]

Simple Summary: Simple Summary: Embryo reinsertion into the same donor mare after embryo flushing would be useful for some reproductive techniques. However, this procedure has been unsuccessful in the past. This study envisages to gain insights into the mechanisms by which embryos fail after embryo flushing and reinsertion in the same mare. The results of this study showed that embryo mortality after embryo reinsertion is not due to luteal deficiency. In contrast, it seems that changes in the endometrial environment due to bacterial contamination and/or inflammation during the uterine lavage are more likely to be responsible for the destruction of most reinserted embryos. The effect of embryo reinsertion immediately after embryo flushing was studied. In Experiment 1, eight mares were used during 32 cycles (8 cycles in each group). For the first two groups, inseminated mares were flushed 8 days after ovulation and prostaglandin F2α was not administered: in group EF-ET (embryo flushing and embryo transfer) the embryo was reinserted in the same donor mare, while in the EF group, no further procedure was performed. In the third group (ET), non-inseminated mares (recipients) received a Day 8 embryo. Progesterone concentration was measured before EF/ET and 72 h after in the three groups. In Experiment 2, twelve mares were used during 17 cycles in two groups, EF-ET (n = 11) and ET (n = 6), as in Experiment 1, except that every mare was flushed 24 h after embryo transfer to retrieve the embryo. Fewer pregnancies resulted after transfer in EF-ET cycles (0/8, 0%) than in the ET group (6/8, 75%). Progesterone concentration decreased significantly (p = 0.05) 72 h after EF-ET but not in EF or ET cycles (p > 0.1). Three mares from the EF-ET showed full luteolysis and signs of endometritis. In Experiment 2, more (5/6; p = 0.08) grade 1 embryos were recovered in the ET compared to the EF-ET group (3/7); 4 embryos were graded 3–4 (were broken or had signs of degeneration) in the EF-ET group but none in the ET group. In both groups, capsule fragments were obtained as indicative of the presence of a recently destroyed embryo in the EF-ET (n = 3) and ET (n = 1) groups. Positive bacterial cultures were obtained in 2/11 and 1/6 embryo flushes from the EF-ET and ET groups, respectively. [ABSTRACT FROM AUTHOR]

The possibility of embryo cryopreservation is important for applying the genome resource banking (GRB) concept to those mammalian species that exhibit embryonal diapause in their early development. Odc1 encodes ODC1, which is a key enzyme in polyamine synthesis. RhoA is an essential part of Rho/ROCK system. Both Odc1 and RhoA play an important role in preimplantation embryo development. Studying these systems in mammalian species with obligate or experimentally designed embryonic diapause may provide insight into the molecular machinery underlying embryo dormancy and re‐activation. The effect of cryopreservation procedures on the expression of the Odc1 and RhoA in diapausing embryos has not been properly studied yet. The purpose of this work is to address the possibility of cryopreservation diapausing embryos and to estimate the expression of the Odc1 and RhoA genes in diapausing and non‐diapausing embryos before and after freeze–thaw procedures using ovariectomized progesterone treated mice as a model. Both diapausing and non‐diapausing in vivo‐derived embryos continued their development in vitro after freezing–thawing as evidenced by blastocoel re‐expansion. Although cryopreservation dramatically decreased the expression of the Odc1 and RhoA genes in non‐diapausing embryos, no such effects have been observed in diapausing embryos where these genes were already at the low level before freeze–thaw procedures. Future studies may attempt to facilitate the re‐activation of diapausing embryos, for example frozen–thawed ones, specifically targeting Odc1 or Rho/ROCK system. [ABSTRACT FROM AUTHOR]

Purpose: To assess the relation between number of inseminated oocytes and cumulative live birth rate (CLBR) in order to provide guidance for limiting the number of surplus blastocysts. Methods: The study was a retrospective, single-center cohort analysis of 1223 ART complete cycles. Cycles were stratified according to female age (≤ 34, 35–38, and 39–42 years) and number of inseminated oocytes (1–5, 6–10, and > 10). Inclusion criteria were indication for IVF/ICSI with own spermatozoa and blastocyst culture up to day 6 of all embryos. Results: In patients younger than 35 years, insemination of more than ten oocytes produced an increase in overall blastocyst number, CLBR (40.3%, 54.3%, and 75.8%, respectively, for each oocyte group) and surplus embryo rate (12.9%, 27.8%, and 49.7% of cases for each group). Instead, in the middle age group, the use of more than ten oocytes was solely associated with an increase in the rate of surplus embryos (1.25%, 21.33%, and 28.68% of cases after stratification for oocyte number). In older patients, neither CLBR (9.1%, 23.9%, and 24.7%, respectively) nor rate of surplus embryos (2.0%, 7.1%, and 13.4% of cases for each group) were higher in cycles with more than ten inseminated oocytes. Conclusion: In women up to 38 years, sustainable CLBR are achieved while limiting the number of inseminated oocytes and the resulting blastocysts remaining unused. Based on this notion, novel treatment strategies could pursue high outcome rates, while alleviating the problems derived from surplus stored embryos. [ABSTRACT FROM AUTHOR]

Embryonal diapause is a characteristic feature of about 130 mammalian species. However, very few studies have addressed cryopreservation of diapausing embryos. This work is aimed to apply program freezing to blastocysts obtained from CD1 mice, which were at diapause state after ovariectomy and the subsequent hormonal therapy. Blastocysts collected from non-operated mice of the same strain served as controls. Some diapausing as well as non-diapausing frozen-thawed blastocysts demonstrated blastocoel re-expansion after 24 h of in vitro culture (IVC) indicating their viability after cryopreservation. Raman spectroscopy assessment of phenylalanine accumulation revealed that the fraction of new synthesized proteins was lower for non-frozen as well as for frozen-thawed diapausing blastocysts compared to non-diapausing ones. Although protein metabolism was reduced in diapausing embryos, most of the protein synthesis remained active. Cell number increased after 24 h of IVC in non-frozen as well as in the frozen-thawed blastocysts of the control but not of the diapause group. However, cell numbers were increased in frozen-thawed diapausing blastocysts after 47 h of IVC in a medium supplemented with putrescine. This indicates viability of frozen-thawed diapausing embryos after cryopreservation. Besides, protein metabolism was not affected by cryopreservation in diapausing and non-diapausing murine embryos indicating their viability. Our results demonstrated the possibility of successful cryopreservation of diapausing murine embryos. • Diapausing murine embryos survived cryopreservation. • Protein metabolism was reduced in diapausing murine embryos although remained active. • Protein metabolism was not affected by cryopreservation in diapausing murine embryos. [ABSTRACT FROM AUTHOR]

Purpose: The introduction of the time-lapse monitoring system (TMS) and the development of predictive algorithms could contribute to the optimal embryos selection for transfer. Therefore, the present study aims at investigating the efficiency of KIDScore and iDAScore systems for blastocyst stage embryos in predicting live birth events. Methods: The present retrospective study was conducted in a private IVF Unit setting throughout a 10-month period from October 2021 to July 2022, and included the analysis of 429 embryos deriving from 91 IVF/ICSI cycles conducted due to infertility of various etiologies. Embryos incubated at the Embryoscope+ timelapse incubator were analyzed through the established scoring systems: KIDScore and iDAScore®. The main outcome measure was the comparison of the two scoring systems in terms of live birth prediction. Embryos with the higher scores at day 5 (KID5 score/iDA5 score) were transferred or cryopreserved for later use. Results: Embryos with high KID5 and iDA5 scores positively correlated with the probability of successful live birth, with KID5 score yielding a higher efficiency in predicting a successful reproductive outcome compared to a proportionally high iDA5 score. KID5 demonstrated conservative performance in successfully predicting live birth compared to iDA5 score, indicating that an efficient prediction can be either provided by a relatively lower KID5 score or a relatively higher iDA5 score. Conclusion: The developed artificial intelligence tools should be implemented in clinical practice in conjunction with the conventional morphological assessment for the conduction of optimized embryo transfer in terms of a successful live birth. [ABSTRACT FROM AUTHOR]

Background: Evidence from the Istanbul consensus workshop suggests correlations between morphological parameters and embryo developments. 8-cell embryos are the best blastomere stage on day 3. No good quality evidence exists to support high-quality embryonic selection following blastulation and clinical outcomes. This study aimed to investigate the factors that affect blastocyst formation, blastocyst quality, and clinical outcomes of high-quality cleavage-stage embryos in fresh cycles. Methods: This study was a retrospective analysis of 9608 high-quality cleavage-stage embryos from 2987 couples between January 2017 to June 2021, namely 1520 embryos categorized as "812" (8-cell, grade 2, mild fragmentation), 2961 as "821" (8-cell, grade 2, mild asymmetry), 896 as "711" (7-cell, grade 1), and 517 as "911" (9-cell, grade 1) compared with 3714 embryos categorized as "811" (8-cell, grade 1). The primary outcomes were clinical pregnancy rate (CPR) and live birth rate (LBR). Blastulation rate (BR), available late blastocyst rate (ABR) and high-quality late blastocyst rate (HBR) were secondary outcome measures. Results: BR, ABR, and HBR had significant differences among the five groups (P < 0.001), while CPR and LBR were also significantly different in cleavage-stage fresh transfer (P < 0.01). The multivariable multilevel logistic regression analysis revealed a significant association between cell number, cell size, blastocyst development and clinical outcomes. For 7 to 9-cell highest-quality embryo, mild fragmentation and more blastomeres were more conducive to blastocyst formation and clinical outcomes. While cleavage-stage embryos developed into blastocysts, the negative impact of their initial morphology on clinical outcomes would be erased. Conclusions: Our study firstly evaluated blastocyst development and clinical outcomes of high-quality cleavage-stage embryos in fresh cycles, with rankings of 811, 812, 911, 821, and 711. We found the initial morphological characteristics of the high-quality cleavage-stage embryos did not adversely impact clinical outcomes, even as they progressed to the blastocyst stage. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether embryo cryopreservation is associated with a difference in maternal serum analyte levels in singleton and twin pregnancies conceived via in vitro fertilization (IVF). Methods: This was a retrospective cohort study of singleton and twin pregnancies conceived via IVF from a university health system from 01/2014 to 09/2019. Patients with available first and second trimester serum analyte data were included and analyzed separately. Multiple of the median (MoM) values for free β-human chorionic gonadotropin (β-hCG), pregnancy-associated plasma protein A, alpha-fetoprotein (AFP), Inhibin A, and unconjugated estriol (uE3) were compared between two groups: pregnancies conceived after the transfer of fresh embryos versus pregnancies conceived after the transfer of frozen-thawed embryos. Multiple linear regression of log MoM values with F test was performed to adjust for potential confounders. Results: For singletons, fresh embryos were associated with a lower median first trimester free β-hCG (1.00 MoM vs. 1.14 MoM; parameter estimate [PE] 0.90, 95% CI 0.82–0.99, p =.03) compared to frozen-thawed embryos. Fresh embryos were also associated with a lower median second trimester uE3 (0.93 MoM vs. 1.05 MoM; PE 0.88, CI 0.83–0.95, p =.0004) and AFP (1.02 MoM vs. 1.19 MoM; PE 0.91, CI 0.84–0.99, p =.02) compared to frozen-thawed embryos in singletons. There were no significant differences between median first and second trimester serum analytes in twin pregnancies compared between the two groups. Conclusion: Singleton pregnancies derived from fresh embryos had lower first (free β-hCG) and second (uE3 and AFP) trimester analytes compared to frozen-thawed embryos. Twin pregnancies demonstrated no difference between the groups. [ABSTRACT FROM AUTHOR]

An experiment was conducted to determine whether administration of mycobacterium cell wall fraction (MCWF; Amplimune, NovaVive) could enhance embryo developmental competence following in vitro embryo production (IVP) and pregnancy establishment after embryo transfer (ET). Nulliparous, Holstein heifers (n = 40; age 8–15 months) were submitted to two rounds of ovum pick-up (OPU) and IVP in a crossover design. Thirty-six h after follicle wave synchronization, treatments (saline or MCWF, 5 mL, im) were administered in conjunction with a single dose of follicle stimulating hormone (175 IU) and OPU was performed 48–52 h later. Recovered cumulus-oocyte complexes were used for IVP to assess embryo development. For ET, nulliparous, Holstein heifers (n = 225; age 12–18 months) were used as recipients. At 12–24 h after detection of spontaneous estrus, recipients were randomly treated with either saline or MCWF (5 mL, im). The effect of MCWF on pregnancy per ET (P/ET) was assessed in a 2 × 2 factorial design with recipients treated with or without MCWF receiving a fresh IVP embryo from a donor treated with or without MCWF at day 7 or 8 after detected estrus. Blood samples were collected from a subset of donors (n = 8) and recipients (n = 26 to 33 per treatment) prior to treatment and at 6 and 24 h post-treatment to determine serum concentration of interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and interferon-γ. Blood samples were also collected from a group of recipients (n = 31 to 39 per treatment) to assess serum concentration of progesterone at days 4, 7, and 16 post-treatment. Pregnancy status was determined at days 40 and 100 of gestation. Donor treatment with MCWF tended (P < 0.07) to increase the proportion of oocytes that developed into transferable embryos, but there was no effect of MCWF on other parameters of embryo development. The P/ET at days 40 and 100 of gestation and pregnancy loss were not affected by donor treatment or recipient treatment with MCWF and there was no interaction. Serum concentration of proinflammatory cytokines among donors and recipients and serum concentration of progesterone among recipients were not increased by treatment with MCWF. Results of the present study indicate that treatment of donors with MCWF has minimal impact on subsequent embryo development following IVP. Moreover, regardless of whether donors or recipients were treated with MCWF, there was no effect on P/ET following transfer of IVP embryos. • Donor treatment with MCWF tended to increase the proportion of transferable embryos. • The P/ET was not affected by transfer of embryos from donors treated with MCWF. • There was no effect of recipient treatment with MCWF on P/ET. • Efficacy of IVP-ET was not improved by administration of MCWF. [ABSTRACT FROM AUTHOR]

Research question: Can a strategy for scoring oocyte quality, based on cumulus cell (CC) gene expression, prioritize oocytes with the highest implantation potential, while limiting the number of embryos to be processed in culture and the number of supernumerary embryos to be vitrified? Design: An interventional, blinded, prospective cohort study was retrospectively analyzed. In the original study, patients underwent a fresh Day3 single embryo transfer with embryos ranked based on morphology and CC gene expression (Aurora Test). The additional ranking of the embryos with the Aurora Test resulted in significant higher clinical pregnancy and live birth rates. Now it is investigated if the Aurora Test ranking could be applied to select oocytes. The effect of an Aurora Test based restriction to 2 and 3 2PN or MII oocytes on clinical pregnancy and other outcomes, was analyzed in two subsets of patients with all 2PN (n = 83) or all MII oocytes (n = 45) ranked. Results: Considering only the top three ranked 2PN oocytes, 95% of the patients would have received a fresh SET on Day3 resulting in 65% clinical pregnancies. This was not different from the pregnancy rate obtained in a strategy using all oocytes but significantly reduced the need for vitrification of supernumerary embryos by 3-fold. Considering only top-ranked MII oocytes gave similar results. Conclusions: In countries with legal restrictions on freezing of embryos, gene expression of CC can be used for the selective processing of oocytes and would thus decrease the twin pregnancy rate and workload, especially for embryo morphology scoring and transfers as the handling and processing of lower competence oocytes is prevented, while improving the ART outcome. [ABSTRACT FROM AUTHOR]

Background: Erythropoietin (Epo) is a potent vascular growth factor that induces angiogenesis and antiapoptotic signalling. We investigated whether the development of numerous follicles and corpora lutea during in vitro fertilization (IVF) cycle affects circulating Epo levels and further, if Epo could be used as a novel marker for ovarian hyperstimulation syndrome (OHSS). Methods: 24 women were included in the uncomplicated IVF group and 35 women in the OHSS group. Repeated blood samples from both groups were analysed for Epo, progesterone, blood haemoglobin, and creatinine. Follicular fluid from the IVF group was analysed for Epo and progesterone. Repeated measure analysis was performed for the variables and circulating Epo levels were compared between the IVF group and early OHSS. Furthermore, related growth factors, vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1 (HIF-1) were analysed from subgroup of women to test for correlation with Epo. Results: During IVF, circulating Epo increased from natural mid-luteal phase to stimulated mid-luteal phase (median 9.5; 95% CI 7.2–13.4 IU/L and 12.5; 10.3–13.4 IU/L; p = 0.003). In cycles resulting in pregnancy, Epo level decreased 14 days after oocyte pick-up (OPU) and remained low thereafter. In cycles not resulting in pregnancy, Epo level increased again 35 days after OPU. Follicle fluid Epo concentration was 1.5 times higher than the serum concentration (median 15.4; 95% CI 10.4–19.2 IU/L vs. 10.2; 8.8–12.7; p = 0.006). There was no difference in circulating Epo concentration between early OHSS and uncomplicated IVF. Circulating Epo did not correlate with VEGF or HIF-1. Conclusions: Circulating Epo levels fluctuate during IVF cycle. We hypothesise this may suggest Epo's involvement in ovarian physiology and angiogenesis. However, Epo was not a clinical marker for OHSS. [ABSTRACT FROM AUTHOR]

The widespread use of cryopreserved in vitro produced (IVP) bovine embryos is limited due to their low post-warming viability compared to their ex vivo derived counterparts. Therefore, the present study aimed to analyse in detail the consequences of cryopreservation (vitrification and slow freezing) on the bioenergetic profile of the embryo and its mitochondria. To accomplish that, day 7 IVP embryos were separated in a non-cryopreserved control group (fresh, n = 120, 12 replicates) or were either slow frozen (slow frozen, n = 60, 6 replicates) or vitrified (vitrified, n = 60, 6 replicates). An in-depth analysis of the bioenergetic profiles was then performed on these 3 groups, analysing pools of 10 embryos revealing that embryo cryopreservation both via vitrification and slow freezing causes profound changes in the bioenergetic profile of bovine embryos. Noteworthy, fresh embryos demonstrate a significantly (P < 0.05) higher oxygen consumption rate (OCR) compared to vitrified and slow frozen counterparts (0.858 ± 0.039 vs. 0.635 ± 0.048 vs. 0.775 ± 0.046 pmol/min/embryo). This was found to be largely due to significantly reduced mitochondrial oxygen consumption in both vitrified and deep-frozen embryos compared to fresh counterparts (0.541 ± 0.057 vs. 0.689 ± 0.044 vs. 0.808 ± 0.025 pmol/min/embryo). Conversely, slow-frozen thawed blastocysts showed 1.8-fold (P < 0.05) higher non-mitochondrial OCR rates compared to fresh embryos. Maximum mitochondrial respiration of vitrified and slow-frozen embryos was significantly reduced by almost 1.6-fold compared to fresh embryos and the proportion of ATP-linked respiration showed significantly lower values in vitrified thawed embryos compared to fresh embryos (1.1-fold, P < 0.05). Likewise, vitrification-warming and freeze-thawing reduced reactive glycolytic capacity (1.4 fold, 1.2-fold)as well as compensatory glycolytic capacity to provide energy in response to mitochondrial deficiency (1.3-fold and 1.2-fold, P < 0.05). In conclusion, the present study has, to the best of our knowledge, identified for the first time a comprehensive overview of typical altered metabolic features of the bioenergetic profile of bovine embryos after cryopreservation, which have great potential to explain the detrimental effects of cryopreservation on embryo viability. Avoidance of these detrimental effects through technical improvements is therefore suggested to be mandatory to improve the viability of bovine embryos after cryopreservation-warming. • Vitrification-warming and Freeze-thawing of bovine embryos profoundly affects the bioenergetics profile. • Vitrified and slow frozen bovine embryos demonstrate a significantly lower oxygen consumption rate compared to fresh embryos. • Vitrified and slow frozen bovine embryos show a significantly lower mitochondrial oxygen consumption rate than fresh embryos. • Maximum mitochondrial respiration of vitrified and slow-frozen embryos is reduced compared to fresh embryos. • Vitrification-warming and freeze-thawing of bovine embryos reduce the reactive glycolytic capacity compared to fresh embryos. [ABSTRACT FROM AUTHOR]

Purpose: Are trends in singleton donor oocyte IVF perinatal outcomes consistent over time among four international ethnically diverse infertility centers? Methods: This retrospective cohort consisted of an infertility network of four international IVF centers across three continents. Singleton live births resulting from fresh and frozen donor oocyte embryo transfers from January 1, 2012 to December 31, 2018 were included. The main outcome measures were birth weight (BW), preterm birth (PTB), large for gestational age (LGA), small for gestational age (SGA) and gestational age (GA) at delivery. Results: The entire cohort (n = 6640) consisted of 4753 fresh and 1887 frozen donor oocyte embryo transfers. Maternal age, parity, body mass index, neonatal sex and GA at delivery were similar for fresh and frozen donor oocyte embryo transfers in the entire cohort and within each infertility center. All four centers had a trend of decreased BW and rates of PTB before 32 weeks annually, although significance was not reached. Three of the four centers had annual increased trends of PTB before 37 weeks and LGA newborns, although significance was not reached. BWs for the entire cohort for fresh and frozen donor embryo transfers were 3166 g ± 601 g and 3137 g ± 626 g, respectively. Conclusion: Similar trends in perinatal outcomes were present across four international infertility centers over 7 years. The overall perinatal trends in donor oocyte IVF may be applicable to centers worldwide, but further studies in more geographic regions are needed. [ABSTRACT FROM AUTHOR]

In vitro fertilization and production of bovine embryos in vitro is method, which improves utilization of animal reproduction potential. In connection with cryopreservation methods and ability of long-term cryostorage of embryos offers suitable tool for positive influence of endangered species or breeds. In vitro embryo production with subsequent embryo transfer contributes to the improvement of reproduction rates and bypassing some reproduction failure in high productive animal breeding. The method is generally used for in vitro production of transferable bovine embryos. Worldwide about 411 000 of IVP bovine embryos are annually transferred to recipients (IETS, 2013). Most of them were transferred immediately after producing, which is difficult for organization and synchronization of animals. In contrast to this possibility the storage of embryos for later using brings undisputable advantages. In order to protect animal genetic resources and to preserve the gene pool of rare and endangered animals, it is necessary to establish gene banks containing stocks of gametes and embryos of these animals. Optimization of the methods of in vitro production of bovine embryos and increasing their resistance to cryopreservation process is an actual challenge to ensure long-term storage in the gene bank of animal resources. The main goal of this mini-review is to provide general insight into the task of oocyte and embryo resistance to cryopreservation. [ABSTRACT FROM AUTHOR]

Simple Summary: The in vitro production of mammalian embryos generates oxidative molecules known as reactive oxygen species that damage the cells developed in in vitro cultures because of the culture system itself and other biotechnologies commonly used for animal- assisted reproduction, such as cryopreservation of embryos by vitrification. That is why antioxidants must be added to the in vitro system. Thus, we evaluated if the addition of a particular antioxidant (resveratrol) to the oocytes when they were matured in vitro and then used for producing embryos by in vitro fertilization and vitrification could protect the embryos from the damage caused by vitrification. The results showed that resveratrol, when added to the culture media of oocytes matured in vitro, protects embryos produced by in vitro fertilization from damage caused by vitrification by decreasing reactive oxygen species levels and facilitating the generation of the embryo antioxidant enzymes like glutathione. This means that resveratrol can be used to help embryos overcome vitrification damage. The in vitro production and cryopreservation of mammalian embryos generates reactive oxygen species (ROS) due to conditions of the system that can overcome their antioxidant protection. Resveratrol is an antioxidant used in in vitro systems to improve blastocyst rates, but its effect on antioxidant enzymes such as glutathione (GSH) in embryos produced by in vitro fertilization (IVF) after vitrification has not been reported. The objective of this study was to evaluate the effects of resveratrol on the in vitro maturation medium (IVM) of sheep oocytes (Ovis aries) on the levels of ROS and GSH in embryos produced by IVF subjected to vitrification. Resveratrol was added at 0 µM, 0.25 µM, 0.5 µM, and 1 µM during oocyte in vitro maturation (IVM). Matured oocytes were fertilized with thawed ram sperm. Embryos were cultured in sequential media until blastocysts, were then vitrified for 24 h, and, after heating, they were stained with DCFH-DA (2′,7′-dichlorodihydrofluorescein diacetate) to determine the presence of ROS and with Cell Tracker Blue® for the presence of GSH. The quantitative values of ROS and GSH were obtained through the Image J image processor. The results showed that resveratrol increased GSH and decreased ROS production (p < 0.05) in a dose-dependent manner. It is concluded that its use in sheep oocytes during IVM has a beneficial effect on embryos produced by IVF subjected to vitrification by decreasing reactive oxygen species levels and facilitating the generation of embryo antioxidant enzymes like glutathione. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to evaluate the cumulative live birth rate (CLBR) of mild stimulation and conventional stimulation for the low-prognosis population undergoing PPOS protocols. Methods: This was a retrospective cohort study. We included women with a low prognosis. All women underwent PPOS protocols, and the starting gonadotropin (Gn) dose was 150 IU or 300 IU. The primary outcome measure was CLBR. The secondary outcome measures were the number of oocytes retrieved, number of 2PN oocytes and number of available embryos. Results: In total, 171 women with mild stimulation and 1810 women with conventional stimulation met the criteria. In the PSM model, 171 mild stimulation cycles were matched with 513 conventional stimulation cycles. The gonadotropin dosage in the mild stimulation group was significantly lower than that in the conventional stimulation group (1878.6 ± 1065.7 vs. 2854.7 ± 821.0, P<0.001). The numbers of oocytes retrieved, 2PN oocytes, available embryos and high-quality embryos were also higher in the conventional stimulation group than in the mild stimulation group (P<0.05). There was no significant betweengroup difference in the cumulative clinical pregnancy rate (26.3% vs. 27.5%, P=0.77). The CLBR after mild stimulation was similar to that after conventional stimulation (21.1% vs. 22.0%, P=0.79). Conclusion: In our study, we found that the CLBRs of mild stimulation and conventional stimulation were similar, despite conventional stimulation resulting in significantly more oocytes and embryos. Thus, mild stimulation can be considered an option for women with a low prognosis in PPOS protocols. [ABSTRACT FROM AUTHOR]

Introduction: The delayed-start gonadotropin-releasing hormone antagonist protocol seems effective for patients who are poor ovarian responders, but there are insufficient data on whether it is also effective for patients with poor-quality embryos and low rates of good blastocyst formation. Specifically, the effectiveness of delayed-start gonadotropin-releasing hormone antagonists with progesterone has not been adequately investigated. Therefore, we compared the efficacy of the original delayed-start gonadotropin-releasing hormone antagonist protocol using medroxyprogesterone acetate (MPA) and high-dose gonadotropin in patients with poor ovarian response. Methods: Overall, 156 patients with recurrent assisted reproductive technology failure who underwent the original protocol were included. They received cetrorelix acetate (3 mg) and MPA (10 mg) on cycle day 3, and high-dose gonadotropin was initiated on day 11. When the leading follicle reached 14 mm, ganirelix acetate (0.25 mg) was administered until the trigger day. The number of oocytes retrieved, metaphase II (MII) oocytes, two pronuclear (2PN) zygotes, and good blastocysts and live birth rates were compared between the previous (Cycle A) and original (Cycle B) cycles in three groups (Group A, all patients; Group B, poor responders; and Group C, patients with poor-quality embryos). Results: In Group A (n=156), the number of MII oocytes (3.6 ± 3.3 versus 4.5 ± 3.6), 2PN zygotes (2.8 ± 2.9 versus 3.8 ± 3.1), good blastocysts (0.5 ± 0.9 versus 1.2 ± 1.6), and live birth rates (0.6 versus 24.4) significantly increased in Cycle B. Similar results were obtained in Group B (n=83; 2PN zygotes [1.7 ± 1.7 versus 2.3 ± 1.8], good blastocysts [0.4 ± 0.7 versus 0.9 ± 1.3], live birth rates [0 versus 18.1]) and Group C (n=73; MII oocytes [5.1 ± 3.8 versus 6.6 ± 4.0], 2PN zygotes [4.0 ± 3.4 versus 5.4 ± 3.4], good blastocysts [0.7 ± 1.1 versus 1.6 ± 1.9], and live birth rates [1.4 versus 31.5]). Conclusion: This original protocol increased the number of MII oocytes retrieved, 2PN zygotes, good blastocysts, and live birth rates in both poor responders and in patients with poor-quality embryos. [ABSTRACT FROM AUTHOR]

One of the approaches to improve cryotolerance in lipid-rich embryos is to modify their lipidome in vitro. This work is aimed to study the effects of forskolin exposure on the in vitro embryo development of the domestic cat and to evaluate how the change in lipid content affects the cryopreservation results. In vitro -derived embryos were cultured with 10 μM forskolin from the 2-cell stage for 24 h or 96/168 h to the morula/blastocyst stage. Some of the embryos treated with forskolin for 24 h were cryopreserved with slow freezing, the other ones were used to characterize their developmental rates and the amount of intracellular lipids. The in vitro exposure to forskolin had a positive effect on the embryo development, as more embryos developed to the morula stage in the forskolin-treated group (92.9%) compared to the controls (64.7%) after 120 h of in vitro culture (IVC). Nile Red staining revealed a reduced amount of intracellular lipids in the forskolin-treated embryos. The percentage of embryos developed to the morula stage was lower in the frozen-thawed embryos not treated with forskolin (54.5%), but not in the frozen-thawed forskolin-treated group (63.6%) as compared to non-frozen controls (80.8%). Thus, the exposure of embryos to forskolin in vitro reduced the level of intracellular lipids and affected embryo development before and after cryopreservation. • Forskolin treatment reduces the level of the intracellular lipids in the cat embryo cells. • Short-term and long-term exposure to forskolin enhanced embryo developmental rate up to morula stage. • Forskolin-treated preimplantation cat embryos tolerated cryopreservation better than control non-treated ones. [ABSTRACT FROM AUTHOR]

Introduction: The addition of antagonists is mainly based on estrogen level and follicle size, while LH level has not received sufficient attention.In this study, LH Level on the antagonist administration day was used as the main research objective to explore its relationship with laboratory indicators and pregnancy outcomes. Methods and Analysis: We enrolled 854 patients with normal ovarian function undergoing in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) between May 2021 to May 2022 at the Reproductive Center of Shandong University of Traditional Chinese Medicine.We used the quartile method to group LH levels on the antagonist administration day. There were four groups: Q1 (0.53IU/L≤LH ≤ 1.89IU/L); Q2 (1.89IU/L

Invasive and noninvasive features are normally applied to select developmentally competent oocytes and embryos that can increase the take-home baby rates in assisted reproductive technology. The noninvasive approach mainly applied to determine oocyte and embryo competence has been, since the early days of IVF, the morphological evaluation of the mature cumulus-oocyte complex at the time of pickup, first polar body, zona pellucida thickness, perivitelline space and cytoplasm appearance. Morphological evaluation of oocyte quality is one of the options used to predict successful fertilization, early embryo development, uterine implantation and the capacity of an embryo to generate a healthy pregnancy to term. Thus, this paper aims to provide an analytical revision of the current literature relating to the correlation between ovarian stimulation procedures and oocyte/embryo quality. In detail, several aspects of oocyte quality such as morphological features, oocyte competence and its surrounding environment will be discussed. In addition, the main noninvasive features as well as novel approaches to biomechanical parameters of oocytes that might be correlated with the competence of embryos to produce a healthy pregnancy and live birth will be illustrated. [ABSTRACT FROM AUTHOR]

Louise Brown's birth in 1978 heralded a new era not just in reproductive technology, but in the relationship between science, cells, and society. For the first time, human embryos could be created, selected, studied, manipulated, frozen, altered, or destroyed, outside the human body. But with this possibility came a plethora of ethical questions. Is it acceptable to destroy a human embryo for the purpose of research? Or to create an embryo with the specific purpose of destroying it for research? In an attempt to construct ethical and legal frameworks for the new era of cellular reprogramming, legislators and ethicists have tried to distinguish between different kinds of biological entity. We treat cells differently depending on whether they are human or animal, somatic cells or gametes, and on whether they are embryos or not. But this approach to the ethics of cellular reprogramming is doomed to failure for the simple reason that cellular reprogramming in itself destroys the distinctions that the law requires to function. In this article, we explore the historical trajectory of cellular reprogramming and its relationship with ethics and society. We suggest that the early hype of embryo research has not obviously fulfilled expectations, but since new avenues of research are continuously opening, it is hard to say definitely that these promises have been broken. We explore the forthcoming challenges posed by the creation of DNA from scratch in the laboratory, and the implications of this for understandings of identity, privacy, and reproduction. We conclude that while ethics used to seek answers in biological facts, this is no longer possible, and a new approach is required. [ABSTRACT FROM AUTHOR]

Background: Recurrent implantation failure (RIF) is more common among patients receiving assisted reproductive treatment. Many efforts have been made to increase the incidence of clinical pregnancy among patients with RIF. The effect of the sequential transfer procedure, a two-step interval transfer of a cleavage-stage embryo followed by a blastocyst in one transfer cycle, on the clinical outcomes of RIF patients remains controversial. Methods: In total, 1774 frozen-thawed embryo transfer (FET) cycles in RIF patients were included. Of these cycles, 302 were sequential embryo transfer (ET) cycles, 979 were double day 3 cleavage-stage ET cycles, and 493 were double blastocyst ET cycles. The primary outcomes were the rates of implantation, clinical pregnancy and multiple pregnancy, and the secondary outcomes were the rates of hCG positive, early miscarriage and ectopic pregnancy. Results: The implantation, hCG positive, and clinical pregnancy rates in the sequential ET group (32.1%, 58.9%, 50.7%) were significantly higher than those in the day 3 cleavage-stage ET group (24.9%, 46.5%, 40.4%) and were similar to those in the blastocyst transfer group (30.1%, 56.4%, 47.1%). The early miscarriage rate in the blastocyst transfer group was significantly higher than that in the cleavage-stage ET group (17.2% vs. 8.1%, P <0.05), while the ectopic pregnancy rate in the blastocyst transfer groupwas significantly lower than that in the cleavage-stage ET group (0.4% vs. 3.0%, P <0.05). The multiple pregnancy rate in the sequential ET group was significantly lower than that in the cleavage-stage ET group (17.0% vs. 25.5%, P <0.05) and the blastocyst transfer group (17.0% vs. 27.6%, P <0.05). When cycles of blastocyst culture failure were excluded, the clinical pregnancy rate was significantly higher (55.7% vs. 47.1%, P <0.05), and the early miscarriage rate and multiple pregnancy rate were significantly lower (8.5% vs. 17.2%, 17.7% vs. 27.6%; P <0.05, respectively) in the sequential ET group than in the double blastocyst ET group. Conclusions: Sequential embryo transfer in FET cycles could improve the clinical outcomes of patients with RIF. [ABSTRACT FROM AUTHOR]

The implementation of CRISPR technology in large animals requires further improvements in embryo manipulation and transfer to be applied with commercial purposes. In this study we report (a) developmental competence of CRISPR/Cas microinjected zygotes subjected to in vitro culture in large scale programs in sheep; (b) pregnancy outcomes after early-stage (2–8-cell) embryo transfer into the oviduct or the uterine horn; and (c) embryo survival and birth rate after vitrification/warming of CRISPR/Cas microinjected zygotes. Experiment 1 consisted of a retrospective analysis to evaluate embryo developmental rate of in vitro produced zygotes subjected to CRISPR/Cas microinjection (n = 7,819) compared with a subset of non-microinjected zygotes (n = 701). Development rates to blastocyst on Day 6 were 20.0% for microinjected zygotes and 44.9% for non-injected zygotes (P < 0.05). In Experiment 2, CRISPR/Cas microinjected zygotes were transferred on Day 2 after in vitro fertilization (2-8 cell embryos) into the oviductal ampulla (n = 262) or into the uterine horn (n = 276) in synchronized recipient ewes at prefixed time (i.e., approximately two days after ovulation). Pregnant/transferred recipients (24.0% vs. 25.0%), embryo survival/transferred embryos (6.9% vs. 6.2%), and born lambs/pregnant embryos (72.2% vs. 100.0%) did not differ significantly in the two groups. In Experiment 3, CRISPR/Cas microinjected zygotes were maintained under in vitro culture until blastocyst stage (Day 6), and subjected to vitrification/warming via the Cryotop method (n = 474), while a subset of embryos were left fresh as control group (n = 75). Embryos were transferred into the uterine horn of recipient females at prefixed time 8.5 days after the estrous synchronization treatment (i.e., approximately six days after ovulation). Pregnancy rate (30.8% vs. 48.0%), embryo survival rate (14.8% vs. 21.3%), and birth rate (85.7% vs. 75.0%) were not different (P NS) between vitrified and fresh embryos, respectively. In conclusion, the current study in sheep embryos reports (a) suitable developmental rate after CRISPR/Cas microinjection (i.e., 20%), even though it was lower than non-microinjected zygotes; (b) similar outcomes when Day 2-embryos were placed into the uterine horn instead of the oviduct, avoiding both time-consuming and invasive oviduct manipulation, and extended in vitro culture during one week; (c) promising pregnancy and birth rates obtained with vitrification of CRISPR/Cas microinjected embryos. This knowledge on in vitro embryo development, timing of embryo transfer, and cryopreservation of CRISPR/Cas microinjected zygotes have practical implications for the implementation of genome editing technology in large animals. • Acceptable in vitro embryo development rate after CRISPR/Cas microinjection. • Similar outcomes when Day 2-embryos are placed into the uterine horn vs. ampulla. • Promising pregnancy and birth rates obtained with vitrified CRISPR/Cas embryos. [ABSTRACT FROM AUTHOR]

Electroreception is an intriguing sense in the animal kingdom, that confers an advantage, when other senses cannot be used. Many shark and ray species spend a prolonged embryonic life stage enclosed in an egg case, where the avoidance of predators is difficult. In this study, we found that late stages of small-spotted catshark (Scyliorhinus canicula) exhibit a freeze response that stops ventilation when exposed to electric stimuli. The embryos also showed a short-term tolerance buildup, when exposed to several electrical stimuli over a 40-min period. Surprisingly, the embryos also reacted with a freeze response when the electrical field was turned off, indicating that the embryos reacted to a change in electrical field, rather than the presence of one. Younger embryos showed a significantly longer freeze response than older embryos. This study documents the use of electroreception in small-spotted catshark embryos as a possible predator avoidance response. [ABSTRACT FROM AUTHOR]

Selection of competent recipients before embryo transfer (ET) is indispensable for improving pregnancy and birth rates in cattle. However, pregnancy prediction can fail when the competence of the embryo is ignored. We hypothesized that the pregnancy potential of biomarkers could improve with information on embryonic competence. In vitro-produced embryos cultured singly for 24 h (from d 6 to 7) were transferred to d 7 synchronized recipients as fresh or after freezing and thawing. Recipient blood was collected on d 0 (estrus; n = 108) and d 7 (4–6 h before ET; n = 107) and plasma was analyzed by nuclear magnetic resonance (1H+NMR). Spent embryo culture medium (CM) was collected and analyzed by ultra-high-performance liquid chromatography tandem mass spectrometry in a subset of n = 70 samples. Concentrations of metabolites quantified in plasma (n = 35) were statistically analyzed as a function of pregnancy diagnosed on d 40, d 62 and birth. Univariate analysis with plasma metabolites consisted of a block study with controllable fixed factors (i.e., embryo cryopreservation, recipient breed, and day of blood collection; Wilcoxon test and t -test). Metabolite concentrations in recipients and embryos were independently analyzed by iterations that reclassified embryos or recipients using the support vector machine. Iterations identified some competent embryos, but mostly competent recipients that had a pregnancy incompetent partner embryo. Misclassified recipients that could be classified as competent were reanalyzed in a new iteration to improve the predictive model. After subsequent iterations, the predictive potential of recipient biomarkers was recalculated. On d 0, creatine, acetone and l -phenylalanine were the most relevant biomarkers at d 40, d 62, and birth, and on d 7, l -glutamine, l -lysine, and ornithine. Creatine was the most representative biomarker within blocks (n = 20), with a uniform distribution over pregnancy endpoints and type of embryos. Biomarkers showed higher abundance on d 7 than d 0, were more predictive for d 40 and d 62 than at birth, and the pregnancy predictive ability was lower with frozen-thawed (F-T) embryos. Six metabolic pathways differed between d 40 pregnant recipients for fresh and F-T embryos. Within F-T embryos, more recipients were misclassified, probably due to pregnancy losses, but were accurately identified when combined with embryonic metabolite signals. After recalculation, 12 biomarkers increased receiver operator characteristic-area under the curve (>0.65) at birth, highlighting creatine (receiver operator characteristic-area under the curve = 0.851), and 5 new biomarkers were identified. Combining metabolic information of recipient and embryos improves the confidence and accuracy of single biomarkers. [ABSTRACT FROM AUTHOR]

In this study, it was aimed to determine the effect of destruction of lyophilized and frozen-thawed ram sperm plasma and acrosomal membrane on development of embryos produced by intracytoplasmic sperm injection (ICSI). Semen samples were divided into two groups for lyophilization (L) and freezing (F). For the removal of the plasma membrane, L and F groups were incubated with Triton X-100 (LTX-100 and FTX-100, respectively). Integrities of the plasma membrane, acrosome and chromatin structure were evaluated. Oocytes were injected with these sperm groups. Although no plasma membrane and acrosome integrities of the L (0.0%) group were detected, the plasma membrane integrity of the F group (69.4%) was significantly higher than the FTX-100 group (23.6%) (p < 0.05). The acrosome integrity of the FTX-100 group (3.80%) was significantly lower than the F group (55.6%) (p < 0.05). The chromatin integrities of L and F groups were higher than the Triton X-100 treated groups (p < 0.05). ICSIs with L, LTX-100, F and FTX-100 sperm were produced similar cleavage and blastocyst rates. In conclusion, data presented here confirm that ram spermatozoa can effectively be lyophilized and injected into oocytes for initiation of embryonic development and Triton X-100 pretreatment is not necessary while using lyophilized and frozen semen. [ABSTRACT FROM AUTHOR]

Cryopreservation, for many reasons, has assumed a central role in IVF treatment cycles, which has resulted in rapidly expanding cryopreserved oocyte and embryo inventory of IVF clinics. We aspire to consider how and with what resources and tools "deep" technology can offer solutions to these cryobiology programs. "Deep tech" has been applied as a global term to encompass the most advanced application of big data analysis for the most informed construction of algorithms and most sophisticated instrument design, utilizing, when appropriate and possible, models of automation and robotics to realize all opportunities for highest efficacy, efficiency, and consistency in a process. [ABSTRACT FROM AUTHOR]

In vitro fertilization (IVF) technologies have great potential in the preservation of endangered species. In the current study, an IVF experiment was carried out to evaluate whether reproductive technologies are suitable for Kazakh Whiteheaded cattle, aimed at preserving this breed whose population has reduced drastically over the last thirty years. The reproduction characteristics of Kazakh Whiteheaded cows were compared to Aberdeen Angus cows. Transvaginal ultrasound-guided ovum pick up sessions were carried out followed by in vitro embryo production and embryo transfer and pregnancy diagnosis. The total and viable oocytes per OPU procedure were 12.8 ± 1.18 and 8.7 ± 0.85 for the Aberdeen Angus breed, and 8.8 ± 1.04 and 6.2 ± 0.83 for the Kazakh Whiteheaded breed. Similarly, the mean number of cleaved oocytes and morula/blastocyst stage embryos produced by OPU/IVF were 4.8 ± 0.49 and 1.4 ± 0.15 for the Aberdeen Angus breed, and 2.4 ± 0.46 and 0.18 ± 0.05 for the Kazakh Whiteheaded breed (p ≤ 0.02). From fifty Kazakh Whiteheaded donor animals, 2585 oocytes were aspirated following six ovum pick up sessions. One thousand eight hundred and seventy-six (72.5%) oocytes were chosen for maturation and were further fertilized. The number of embryos cleaved was 720 (38.3% out of oocytes fertilized) on day four post-fertilization. Of these cleaved embryos, 56 (7.5%) developed into the late morula/blastocyst stage on day seven post-fertilization, averaging 1.12 embryos per donor animal. Pregnancy was detected in 12 recipients; 4 healthy calves have been born to date. The outcomes of our study have demonstrated that reproductive technologies can be applicable in preserving the endangered Kazakh Whiteheaded cattle. The findings in this report will enhance knowledge of the reproductive characteristics of endangered domestic animals and help develop sophisticated reproductive protocols for animals with unique reproductive mechanisms. [ABSTRACT FROM AUTHOR]

The authors studied the dynamics of thinning of the zona pellucida (ZP) in mouse embryo as a result of laser-assisted hatching performed at the blastocyst stage. Mouse embryos previously subjected to a freeze–thaw cycle (cryo-embryos) were selected as model embryos. For ZP microsurgery, femtosecond laser pulses were used (radiation wavelength 512 nm, pulse duration 100 fs, intensity 2.5 TW/cm2). The thickness of the ZP was measured before microsurgery at the blastocyst stage (~E3.5, i.e., 3.5 days of embryonic development) and at the hatching stage (~E5). It was found that the ZP of control group embryos (cryo-embryos not subjected to laser exposure) thinned more strongly (from 6.6 (E3.5) to 4.9 µm (E5)) compared to experimental embryos after the laser-assisted hatching procedure (from 7.1 (E3.5) to 6.4 µm (E5)). In both the first and second cases, changes in ZP thickness were statistically significant. The results were compared with data for "fresh" embryos not subjected to cryopreservation. There was no pronounced effect of ZP hardening in cryo-embryos compared to fresh embryos. The use of the laser-assisted hatching procedure for cryo-embryos made it possible to increase the probability of successful hatching compared to embryos in the control group from 38.5 to 52.5%. [ABSTRACT FROM AUTHOR]

Simple Summary: Due to gene pool insufficiency, it is clear to use the best breeds of sheep for meat. Multiple Ovulation and Embryotransfer Technology (MOET) is applied to improve the genetic and production performance of high-value ewes. This article presents cryoresistance data for Charollais sheep embryos, considering the stage of embryo development and the freezing method. No significant differences in survival rate and morphological structure between cryopreserved and fresh embryos were found. But, cryoresistance largely depended on embryonic development stages. Thus, cryopreservation of embryos at the 6 days after insemination was more effective than freezing 2–3-day embryos after insemination. The data obtained is believed to make assisted reproductive technologies (ART) more effective and cheaper. This article will be interesting for farm producers, breeders and researchers. This article presents data from experiments to determine the cryoresistance of Charollais sheep embryos, depending on the stage of embryo development and the method of freezing, as well as the results of embryo transfer. The study design consisted of a study on the cryopreservation of ewe embryos at different developmental stages (early, 2–8 blastomeric and late, at the morula/blastocyst stage), two cryopreservation protocols (slow freezing and ultra-fast vitrification), and embryo transfer of cryo- and fresh embryos. Embryos from Charollais sheep donors (n = 12) were recovered after induction of superovulation. The embryos were recovered surgically (laparotomy) on days 2 and 6 after insemination. Before there was transfer to recipients, part of embryos was cryopreserved using standard slow freezing and ultra-fast vitrification methods. The average ovarian response was 7.54 ovulations per donor, and 5.83 embryos per donor were collected. No effect of the cryopreservation method and embryo development stage on the preservation of the morphological structure of embryos was found. There were no significant differences in the survival rate of cryoembryos at different development stages, frozen using different techniques, and after transfer to recipients. Differences in cryoresistance between embryonic developmental stages in favor of the morula/blastocyst stage were found (survival after thawing 86.4% vs. 75.0% in early embryos). At different stages of development, the survival rate of fresh embryos (45.8%) compared to cryopreserved ones (30.2%) was significantly higher (p < 0.05), while among fresh ones, the best survival rate (50.0%) was observed after the transfer of morules and blastocysts. [ABSTRACT FROM AUTHOR]

Purpose: What is the rate of euploidy and clinical viability of embryos resulting from micro 3 pronuclei zygotes? Methods: Retrospective cohort analysis in a single, academic in vitro fertilization (IVF) center from March 2018 to June 2021. Cohorts were separated by fertilization as either a 2 pronuclear zygote (2PN) or micro 3 pronuclear zygote (micro 3PN). PGT-A was performed to identify embryonic ploidy rates in embryos created from micro 3PN zygotes. The clinical outcomes of all transferred euploid micro 3PN zygotes were evaluated from frozen embryo transfer (FET) cycles. Results: During the designated study period, 75,903 mature oocytes were retrieved and underwent ICSI. Of these, 60,161 were fertilized as 2PN zygotes (79.3%) and 183 fertilized as micro 3PN zygotes (0.24%). Of the micro 3PN-derived embryos that underwent biopsy, 27.5% (n=11/42) were deemed euploid by PGT-A, compared to 51.4% (n=12,301/23,923) of 2PN-derived embryos, p=0.06. Four micro 3PN-derived embryos were transferred in subsequent single euploid FET cycles, which includes one live birth and one ongoing pregnancy. Conclusion: Micro 3PN zygotes that develop to the blastocyst stage and meet the criteria for embryo biopsy have the potential to be euploid by preimplantation genetic testing for aneuploidy (PGT-A) and if selected for transfer can achieve a live birth. Although there are a significantly lower number of micro 3PN embryos that make it to blastocyst biopsy, the potential to continue to culture abnormally fertilized oocytes may give these patients a chance at pregnancy that they previously did not have. [ABSTRACT FROM AUTHOR]

Background: Recently POSEIDON (Patient-Oriented Strategies Encompassing Individualized Oocyte Number) classification was proposed to categorize patients with expected poor response to conventional stimulation. Searching for the ideal management of poor responders in IVF is still an active research area. Aims: This study compares GnRH-antagonist and GnRH-agonist short protocols in ICSI cycles for the POSEIDON-4 group. Settings and Design: This retrospective study was conducted in a tertiary infertility unit between January 2016 and December 2020. Materials and Methods: Infertile women who met the criteria for POSEIDON 4 group and underwent fresh ICSI-ET in using GnRH-antagonist and GnRH-agonist short protocols was performed. POSEIDON-4 includes patients = 35 years with poor ovarian reserve markers; AFC < 5 and AMH < 1.2 ng/ml. Statistical Analysis Used: Numerical variables were compared between both groups by student's t test and Mann Whitney test when appropriate. Chi-square test used to compare categorical variables. Multivariate logistic regression models were utilized to adjust for the effect of the different study confounders on live birth rate. Results: One hundred ninety fresh ICSI cycles were analyzed. Of the total cohort, 41.6 % (79) patients pursued antagonist protocol compared to 58.4% (111) underwent short agonist protocol. Fresh embryo transfer was accomplished in 55.7 % (44/79) vs. 61.3 % (68/111), P = 0.44 in antagonist vs. short protocol respectively. Cycle cancellation due to poor ovarian response was encountered in (32.9%vs. 27.9%, P = 0.50) in the antagonist and short groups, whereas no good-quality embryos were developed after ovum pickup in 11.4% vs. 10.8%, P>0.05. Comparable total gonadotropins dose, number of retrieved and mature oocytes, and good-quality embryos were found in both groups. Likewise, clinical pregnancy rate was not different for the antagonist and short groups [11/79 (13.9%) vs. 20/111 (18%), P = 0.45]. The live birth rate was comparable between both groups (8.9% vs. 10.8%, P = 0.659) for antagonist and short groups respectively. No significant impact for the protocol type on live birth rate was revealed after adjusting to cycle confounders in multivariate analysis (OR: 0.439, 95%CI 0.134-1.434, P = 0.173). Conclusion: This study shows comparable pregnancy outcomes for antagonist and short-agonist protocols in IVF/ICSI cycles for POSEIDON-4 category. [ABSTRACT FROM AUTHOR]

Cells of pre-implantation embryos are equipped with many morphological and functional systems through which they can synthesize specific proteins and effectively ensure the protection of early embryonic development. Here we present evidence for the existence of these systems in morphologically normal and abnormal bovine blastocyst stage embryos in vivo at the ultrastructural and actin cytoskeleton levels. The appearance of organelles in the trophectoderm and inner cell mass (ICM) cells, responsible for their synthetic activities and their role in the development of early bovine embryos are described. We point out the importance of endocytic processes and the participation of extracellular vesicles in the formation of intercellular contacts and homeostasis of the embryo microenvironment. Several changes in the ultrastructural morphology of embryos produced by different methods (ICSI, parthenogenetic AC/DC electrical activation, IVF with separated sperm) and freezing/thawed embryos are described. We also show alterations occurred in the organelles after viral contamination of embryos with BHV-1 and BVDV viruses, and in embryos from over-conditioned cows. Recorded changes in organelles and appearance of cellular autophagic structures (vesicles, multivesicular bodies and autophagolysosomes) may negatively affect embryo metabolism and lead to the emergence of pathological processes in trophectoderm and ICM cells of preimplantation embryos. [ABSTRACT FROM AUTHOR]

Background: Currently, optimal method of ovarian stimulation (OS) to in-vitro fertilization (IVF) in the patients with polycystic ovarian syndrome (PCOS) is unknown. The present research aims to study the efficiency of minimal-OS method in treatment of infertile patients with PCOS and also the effect of gonadotropin type (recombinant FSH (r-FSH) vs. urinary Human menopausal gonadotropin (u-HMG)) on treatment cycles with GnRH-antagonist. Methods: In this randomized controlled trial, a total of 120 eligible patients were randomly allocated into four groups of OS to IVF: minimal-OS with r-FSH, minimal-OS with u-HMG, mild-OS with r-FSH and mild-OS with u-HMG. IVF outcomes of groups were analyzed statically. Results: The statistical analysis showed that there were significant differences among groups regarding stimulation duration (p < 0.0001), number of retrieved oocytes (p < 0.0001), number of obtained embryos (p < 0.0001). There were no statistically significant differences in fertilization rate (p = 0.289) and implantation rate (p = 0.757) among our participants. There were also significant differences among these four groups in terms of clinical pregnancy rate (/ET and /cycles) (p < 0.0001, p = 0.021, respectively) and live birth rate/cycles (p < 0.0001). Also cases of freeze all embryos due to prevention of ovarian hyper stimulation syndrome (OHSS) (p = 0.004). Conclusions: On the basis of present results the minimal-OS with u-HMG may be one of optimal methods of control OS in the patients with PCOS in respect to serum levels of estradiol on the day of triggering final oocyte maturation, total dose of prescribed gonadotropin, the optimal number of oocytes and embryos obtained, rate of clinical pregnancy and the incidence of OHSS risk. Trial registration: NCT, NCT03876145. Registered 15/03/2019. Retrospectively registered, http://www.clinicaltrial.gov/ NCT03876145. [ABSTRACT FROM AUTHOR]

Human menopausal gonadotrophin (hMG) has been reported to produce a comparable superovulatory response to that of follicle stimulating hormone (FSH). Furthermore, hMG has a long half‐life as compared with FSH. The present study was designed to compare hMG administered once daily and FSH administered twice daily over a 4 ‐ day period on superovulatory response of Suffolk ewes. During the mid‐luteal phase, twenty‐four Suffolk donor ewes received intravaginal sponges at day 0 for 12 days. The superovulatory regimens in the Control group (n = 12) and the Treatment group (n = 12) consisted of eight injections of FSH given at twice daily and four injections of hMG given at once daily, respectively. At day 13, the donor ewes were subjected to laparoscopic insemination. Embryos were recovered, classified, and transferred to recipient ewes at day 19. Pregnancy status was determined by ultrasound examination 40 days after transfer. Lambing rate was calculated after all the ewes had delivered. No significant differences were observed between the two groups in terms of the structures recovered, transferable embryos, degenerated embryos, unfertilized oocytes, pregnancy rate and lambing rate. The results showed that once daily injection of hMG can produce a comparable superovulatory response and embryo transfer outcomes to those obtained by twice daily injection of FSH over a 4 ‐ day period. It is feasible that hMG is used to replace FSH and reduce the number of injection treatments in ovine superovulatory regimens. [ABSTRACT FROM AUTHOR]

The ability of sibling embryos to form blastocysts may reflect the developmental potential of the embryos that were transferred into the uterus. The purpose of the study was to investigate whether the development speed of sibling embryos positively reflects the live birth rate following fresh embryo transfer. We examined 1262 cycles of women who underwent day 3 (D3) cleavage embryo transfer in the Peking Union Medical College Hospital in 2015–2020, who were divided into three groups (D5, D5 + D6, and D6) according to blastocyst formation. The live birth rate in patients with blastocysts that formed on D6 was significantly lower than the other two groups (36.1%, 45.6% and 44.7%, P < 0.05). For women with blastocysts that formed on D6, the live birth rate was higher in those with more good quality blastocysts than poor-quality blastocysts (42.4 vs 32.3%, P < 0.05). Multiple regression analysis showed that the blastocyst development speed of sibling embryos was an independent factor affecting live birth after fresh embryo transfer (P < 0.05). We concluded that the blastocyst development speed of sibling embryos may reflect live birth rate following the transfer of D3 cleavage embryos. [ABSTRACT FROM AUTHOR]

The development of reproductive technologies in this species is contributing decisively to the development of rabbit farming and the preservation of genetic resources. Obtaining embryos is an essential step to both genetic diffusion and the preservation of genetic resources from genetic erosion or natural disasters. In rabbits, it is common for embryos to be recovered post-mortem after ovarian hyperstimulation with gonadotrophins, although the quality and number of embryos are variable, affecting the embryo viability and offspring rate by the donor. In vivo embryo production within a conservation programme aims not only to obtain a large number of embryos, but also that they come from a greater number of male and female origins, in order to ensure an adequate representation of the original population. This is why both the quality and quantity of embryos obtained per donor rabbit and the rate of donors with offspring after embryo cryopreservation must be considered, as well as the response of the embryos to the chemical, physical and physiological stress to which they are subjected in the rederivation process and its postnatal repercussions on those that survive. Rederived rabbits from cryopreserved and transferred embryos showed phenotypic growth changes, which calls into question the neutrality of the technique and its usefulness in those cases in which a control population is required. [ABSTRACT FROM AUTHOR]

Background: The success of embryo production is largely determined by the accuracy of making medium formulations that are adapted to the age of embryo growth. It is known that the cryopreservation method is widely used for the vitrification of embryos frozen at -196°C. Aims: This study aimed to analyze the embryonic development of mice (Mus musculus L.) and hamsters using culture and vitrification media. Method: This method uses the preferred guide to reporting items for systematic review and meta-analysis. Results: Based on the search results, a total of 700 articles were obtained which then entered the elimination stage, resulting in 37 articles on the development of mice embryos (M. musculus L.) and hamsters using culture and vitrification media. Conclusion: Thus, it can be concluded that the identification of the embryonic development of mice (M. musculus L.) and hamsters can be used with the use of culture media and the development of vitrification methods. [ABSTRACT FROM AUTHOR]

Purpose: First trimester miscarriage is a major concern in IVF-ET treatments, accounting for one out of nine clinical pregnancies and for up to one out of three recognized pregnancies. To develop a machine learning classifier for predicting the risk of cleavage-stage embryos to undergo first trimester miscarriage based on time-lapse images of preimplantation development. Methods: Retrospective study of a 4-year multi-center cohort of 391 women undergoing intra-cytoplasmatic sperm injection (ICSI) and fresh single or double embryo transfers. The study included embryos with positive indication of clinical implantation based on gestational sac visualization either with first trimester miscarriage or live-birth outcome. Miscarriage was determined based on negative fetal heartbeat indication during the first trimester. Data were recorded and obtained in hospital setting and research was performed in university setting. Results: A minimal subset of six non-redundant morphodynamic features were screened that maintained high prediction capacity. Features that account for the distribution of the nucleolus precursor bodies within the small pronucleus and pronuclei dynamics were highly predictive of miscarriage outcome as evaluated using the SHapley Additive exPlanations (SHAP) methodology. Using this feature subset, XGBoost and random forest models were trained following a 100-fold Monte-Carlo cross validation scheme. Miscarriage was predicted with AUC 0.68 to 0.69. Conclusion: We report the development of a decision-support tool for identifying the embryos with high risk of miscarriage. Prioritizing embryos for transfer based on their predicted risk of miscarriage in combination with their predicted implantation potential is expected to improve live-birth rates and shorten time-to-pregnancy. [ABSTRACT FROM AUTHOR]

Under natural and well-managed conditions, the buffalo has good reproductive and productive indices. However, in vitro embryo production (IVEP) has been used commercially to maximise the number of elite animals. In this species, several factors (donor management, in vitro culture medium, semen, in vitro conditions, embryo transfer) still affect the IVEP results. In addition, the cost of this technique is very high for this purpose. Therefore, more studies, as well as adequate plans, are needed to achieve this objective efficiently. In this review, we discussed the current commercial status, influencing factors (in vivo and in vitro), and the progress and future challenges of IVEP in buffalo. A total of 81 references were used from 1979 to 2022. The relevant data or literature were searched using the following databases: Google, ResearchGate, Science Alert, Science Direct and PubMed, using the following keywords: buffalo oocytes/COCs, buffalo embryos, pregnancy and calving or live birth rate after embryo transfer. The best maturation, cleavage and blastocyst rates in the in vitro production of buffalo embryos were 95.8, 75.2 and 33.4%, respectively. The pregnancy and live birth rates ranged from 22.2% to 43.5% and from 15.3% to 36.5%, respectively, after the transfer of fresh embryos produced in vitro to the recipients. This review will help to contextualise IVEP in buffaloes, as well as create an adequate plan for implementing IVEP in buffaloes. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the impact of embryo banking on the cumulative live birth rate (CLBR) and the time to live birth (TTLB) in poor ovarian responders (POR) according to the Bologna criteria. Methods: A total of 276 infertile women undergoing IVF with POR were included in this retrospective study. They were divided into two groups with (n = 121) or without (n = 155) embryo banking at the discretion of the attending physicians. A total of 656 and 405 stimulation cycles were started in the two groups respectively during the 24 month follow‐up. Results: The biochemical pregnancy, clinical pregnancy, ongoing pregnancy, and live birth rate per transfer were comparable between two groups (p > 0.05). The CLBR was significantly lower in the banking group than in the non‐banking group (31.4% (38/121) and 43.2% (67/151), p < 0.05). TTLB was significantly longer in the banking group (20.5 months vs. 16.0 months, p < 0.001). In the Kaplan–Meier analysis, the cumulative incidence of live birth was significantly lower in the banking group compared with the non‐banking group (Log rank test, chi‐square = 21.958, p < 0.001). Conclusions: Embryo banking in women undergoing IVF with POR based on the Bologna criteria reduces CLBR and lengthens TTLB when compared with no embryo banking. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to examine the embryonic development of human 4‐cell stage embryos after warming with fatty acids (FAs) and to assess the pregnancy outcomes after single vitrified‐warmed cleavage stage embryo transfers (SVCTs). Methods: Experimental study: A total of 217 discarded, vitrified human 4‐cell stage embryos donated for research by consenting couples were used. The embryos were warmed using the fatty acid (FA)‐supplemented solutions (FA group) or nonsupplemented solutions (control group). The developmental rate, morphokinetics, and outgrowth competence were analyzed. Clinical study: The treatment records of women undergoing SVCT in natural cycles between April and September 2022 were retrospectively analyzed (April–June 2022, control group; July–September 2022, FA group). Results: Experimental study: The rate of morphologically good blastocysts was significantly higher in the FA group than in the control group (p = 0.0302). The morphokinetics during cleavage, morula, and blastocyst stages were comparable between the groups. The outgrowth was significantly increased in the FA group (p = 0.0438). Clinical study: The rates of implantation, clinical pregnancy, and ongoing pregnancy after SVCTs were significantly increased in the FA group (p = 0.0223–0.0281). Conclusions: Fatty acid‐supplemented warming solutions effectively improve embryo development to the blastocyst stage and pregnancy outcomes after SVCTs. [ABSTRACT FROM AUTHOR]

Purpose: To study the relationship between clinical outcomes after assisted reproduction and the migration speed of nucleolus precursor bodies (NPBs) in male and female pronuclei (mPN; fPN). Methods: NPB migration speed, embryo ploidy status, and live birth (LB) were retrospectively analyzed in IVF‐derived zygotes. The central coordinates of the mPN, fPN, and NPBs were noted at multiple timepoints. The migration distance of NPBs between two sequential images was measured to calculate NPB migration speed. Results: The NPB migration speeds in mPN and fPN were significantly faster in euploid zygotes than in aneuploid zygotes. In multivariate logistic analysis, NPB migration speed in mPN and the female age were associated with euploidy. The NPB migration speeds in mPN and fPN were also significantly faster in zygotes that led to LB than in zygotes that led to no pregnancy. In a receiver operating characteristic curve analysis of LB by NPB migration speed in mPN, the cut‐off value was 3.74 μm/h (AUC: 0.825, 95%CI: 0.688–0.963). When the zygotes were categorized by this cut‐off value, there were significantly more LBs in zygotes with migration speed ≥ the cut‐off (78.9% vs. 21.1%). Conclusions: Zygotes with quickly migrating NPBs demonstrated the developmental potential to become a baby. [ABSTRACT FROM AUTHOR]

The demise of Roe v. Wade has prompted some state lawmakers to try to redefine legal personhood to begin before birth and even before pregnancy. The sweeping abortion bans passed and pending in the wake of Dobbs pose a threat to reproductive rights that extends beyond abortion. That threat spills over into in vitro fertilization (IVF) and other assisted reproductive technologies (ART). If legislatures designate embryos as legal persons, fertility clinics will be forced to change how they manage embryos, including current standard practices such as pre-implantation genetic testing, storage of unused embryos, and the disposal of those unlikely to have reproductive potential. This essay examines the many ways in which conferring the status of persons under private and public law is likely to impact patients pursuing IVF and clinics practicing ART. [ABSTRACT FROM AUTHOR]

Whether mammalian embryos develop normally under microgravity remains to be determined. However, embryos are too small to be handled by inexperienced astronauts who orbit Earth on the International Space Station (ISS). Here we describe the development of a new device that allows astronauts to thaw and culture frozen mouse 2-cell embryos on the ISS without directly contacting the embryos. First, we developed several new devices using a hollow fiber tube that allows thawing embryo without practice and observations of embryonic development. The recovery rate of embryos was over 90%, and its developmental rate to the blastocyst were over 80%. However, the general vitrification method requires liquid nitrogen, which is not available on the ISS. Therefore, we developed another new device, Embryo Thawing and Culturing unit (ETC) employing a high osmolarity vitrification method, which preserves frozen embryos at −80°C for several months. Embryos flushed out of the ETC during thawing and washing were protected using a mesh sheet. Although the recovery rate of embryos after thawing were not high (24%-78%) and embryonic development in ETC could not be observed, thawed embryos formed blastocysts after 4 days of culture (29%-100%) without direct contact. Thus, this ETC could be used for untrained astronauts to thaw and culture frozen embryos on the ISS. In addition, this ETC will be an important advance in fields such as clinical infertility and animal biotechnology when recovery rate of embryos were improved nearly 100%. [ABSTRACT FROM AUTHOR]

Objective: Preimplantation genetic testing for aneuploidies (PGT-A) is used to determine chromosomal normality and achieve a successful live birth in infertile couples. There is a possible correlation between chromosomal aneuploidy, embryo development and pregnancy rate. This study evaluated the influence of single blastomere biopsy (SBB) on embryo development and pregnancy rates during frozen embryo transfer (FET) and fresh cycles. Materials and Methods: This quasi-experimental study evaluated 115 intracytoplasmic sperm injection (ICSI) cycles, including 443 embryos (6-8 cells) with a grade A on day three, following PGT-A in the fresh or FET cycles from February 2018 to June 2020. In addition, the fresh cycles without PGT were included as a control group (n=166 embryos). SBB was done on day three and was grouped as FET-PGT (n=149) and the fresh-PGT (n=128). Results: There is a more aneuploidy rate in the FET-PGT group compared to the fresh-PGT cycle (36.60% vs. 20.38%, P<0.001). There is a rate of higher development and blastocyst in the control group. While the embryos of PGT groups showed higher degrees of expansion (expansion 5) on day five. 8.6, 8.59, and 9.37% of expansion 3, 4, and 5 in the fresh-PGT embryos, 12.58, 2.78, and 14.84% of expansion 3, 4, and 5 in the FET-PGD embryos compared to 10.84and 33.73% of expansion 3 and 4 in the control group (without expansion 5; P<0.001). There was no significant relationship between 13, 18, and 21 chromosome aneuploidies with blastocyst development competence among the groups (P<0.1). Following embryo transfer (n=97), the spontaneous abortion rate was higher in the FET-PGT cycles compared to the fresh-PGT and control groups (50 vs. 22 and 11%, respectively; P<0.04). Conclusion: The process of SBB following vitrification significantly decreased embryo development and pregnancy outcomes. Therefore, a morphological analysis could not be reliable in selecting chromosomally normal embryos. [ABSTRACT FROM AUTHOR]

Purpose: Does cell loss (CL) after vitrification and warming (V/W) of day 3 embryos have an impact on live birth rate (LBR) and neonatal outcomes? Method: This retrospective analysis includes cleavage stage day 3 embryos vitrified/warmed between 2011 and 2018. Only single vitrified/warmed embryo transfers were included. Pre-implantation genetic screening, oocyte donation, and age banking were excluded from the analysis. The sample was divided into two groups: group A (intact embryo after warming) and group B (≤ 50% blastomere loss after warming). Results: On the total embryos (n = 2327), 1953 were fully intact (83.9%, group A) and 374 presented cell damage (16.1%, group B). In group B, 62% (232/374) of the embryos had lost only one cell. Age at cryopreservation, cause of infertility, insemination procedure, and semen origin were comparable between the two groups. The positive hCG rate (30% and 24.3%, respectively, for intact vs CL group, p = 0.028) and LBR (13.7% and 9.4%, respectively, for intact vs CL group, p = 0.023) per warming cycle were significantly higher for intact embryos. However, LBR per positive hCG was equivalent between intact and damaged embryos (45.6% vs 38.5%, respectively, p = 0.2). Newborn measurements (length, weight, and head circumference at birth) were comparable between the two groups. Multivariate logistic regression showed that the presence of CL is not predictive for LB when adjusting for patients' age. Conclusions: LBR is significantly higher after transfer of an intact embryo compared to an embryo with CL after warming; however, neonatal outcomes are comparable between the two groups. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of two-step denudation on maternal contamination, ploidy concordance between spent embryo culture medium (SCM) and trophectoderm, blastocyst formation, and clinical outcome. Methods: Sibling embryos of the same couple were re-denuded (treatment) and not re-denuded (control) on day 3, and trophectoderm biopsy and SCM collection were performed on day 5/6. Sex chromosomes of 20 pairs of SCM and biopsy samples were analyzed to determine the reduction in maternal contamination. Blastocyst formation, implantation, and ongoing pregnancy rates were analyzed by recruiting 565 cleavage embryos on day 3. A total of 113 SCM samples and their corresponding trophectoderm results were collected for ploidy concordance analysis. Results: The detection rate of XX between the treatment and control groups was significant (12/20 (60.0%) versus 19/20 (95.0%), p = 0.02). Concordance of sex chromosomes between the two groups was significant (17/20 (85.0%) versus 8/19 (42.1%), p = 0.003). There were no significant differences in blastocyst formation rate, implantation rate, and ongoing pregnancy rate between the two groups. Among the 113 pairs of SCM and its corresponding trophectoderm, 37 cases (33.33%) were completely concordant, 39 cases (35.14%) were partially concordant, and 35 cases (31.53%) were discordant. Conclusion: Our results suggest that re-denudation on day 3 reduces the influence of maternal contamination and improves the accuracy of cfDNA detection. Moreover, the procedure had no significant effect on blastocyst formation, implantation, and ongoing pregnancy rates. In addition, the ploidy concordance approached 70% compared with biopsy, which is acceptable but still not ideal. [ABSTRACT FROM AUTHOR]

Results from studies reporting the optimal stimulation duration of IVF-ICSI cycles are inconsistent. The aim of this study was to determine whether, in the presence of early ovulation-triggering criteria, prolonged ovarian stimulation modified the chances of a live birth. This cross-sectional study included 312 women presenting triggering criteria beginning from D8 of ovarian stimulation. Among the 312 women included in the study, 135 were triggered for ovulation before D9 (D ≤ nine group) and 177 after D9 (D > nine group). The issues of fresh +/− frozen embryo transfers were taken into consideration. Cumulative clinical pregnancy and live-birth rates after fresh +/− frozen embryo transfers were similar in both groups (37% versus 46.9%, p = 0.10 and 19.3% versus 28.2%, p = 0.09, respectively). No patient characteristics were found to be predictive of a live birth depending on the day of ovulation trigger. Postponing of ovulation trigger did not impact pregnancy or live-birth rates in early responders. A patient's clinical characteristics should not influence the decision process of ovulation trigger day in early responders. Further prospective studies should be conducted to support these findings. [ABSTRACT FROM AUTHOR]

Supplementation with estradiol (E2) is routinely used in frozen embryo transfer (FET) cycles and embryo age plays an important role in conceiving. This study was to compare the effects of serum E2 levels on pregnancy outcomes between cleavage- and blastocyst-stage FET cycles using hormone replacement therapy. A total of 776 FET cycles (669 couples) performed from January 2016 to December 2019 were included in the present retrospective cohort study. Regarding cleavage-stage embryo transfers, E2 levels on progesterone initiation day were significantly lower in the ongoing pregnancy/live birth (OP/LB) group than in the non-OP/LB group (214.75 ± 173.47 vs. 253.20 ± 203.30 pg/ml; P = 0.023). In addition, there were downward trends in implantation, clinical pregnancy and OP/LB rates with increasing E2 levels. However, in blastocyst-stage embryo transfers, such trends were not observed, and E2 levels were not significant difference between the OP/LB group and the non-OP/LB group (201.66 ± 182.14 vs. 197.89 ± 212.83 pg/ml; P = 0.884). The results suggests that elevated progesterone-initiation-day E2 levels may negatively affect pregnancy outcomes during artificial cleavage-stage embryo transfers. However, it is not necessary to monitor E2 levels when transferring blastocysts in artificial FET cycles. [ABSTRACT FROM AUTHOR]