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Objective: This study aims to determine the impact of assisted hatching (AH) on pregnancy outcomes in vitrified-warmed blastocyst transfers, and evaluate if embryo expansion or morphology influences outcomes., Methods: A retrospective cohort study was performed including vitrified-warmed blastocyst transfers at our clinic between 2013 and 2017. Of the 2165 embryo transfers, 1986 underwent laser AH and 179 were non-assisted hatched (NAH). The primary outcome was live birth. Secondary outcomes included conception, implantation, clinical pregnancy, clinical pregnancy loss, and monozygotic twinning (MZT)., Results: AH and NAH groups had similar rates of conception (38.7% vs 42.1%), implantation (26.2% vs 27.3%), clinical pregnancy (29.1% vs 30.3%), clinical pregnancy loss (24.0% vs 17.8%), live birth (19.9% vs 20.5%), and MZT (2.08% vs 2.86%). Five pairs of dichorionic/diamniotic twins resulted from single embryo transfers. AH of embryos with expansion grades ≤3 was associated with lower rates of conception (32.5% vs 44.3%%, p < 0.05) and clinical pregnancy (24.0% vs 32.8%, p < 0.05)., Conclusion: AH prior to transfer of vitrified-warmed blastocysts was not associated with improved pregnancy outcomes. The identification of dichorionic/diamniotic twins from single blastocyst transfers challenges the previously held notion that dichorionic/diamniotic MZTs can only occur from division prior to the blastocyst stage. Prospective studies are needed to validate the novel finding of lower rates of conception and clinical pregnancy after AH in embryos with lower expansion grade.

Objective: To compare two different blastocyst biopsy protocols., Design: Retrospective single-center cohort study., Settings: Private in vitro fertilization center., Patient(s): The study included 1,670 frozen-thawed embryo transfers (FETs) with preimplantation genetic testing for aneuploidy (PGT-A)., Intervention: None., Main Outcome Measure(s): Survival rate (SR) after thawing, clinical pregnancy rate (CPR), ongoing implantation rate (IR), and live birth rate (LBR)., Result(s): Eight hundred thirty-five FETs with PGT-A cycles including only embryos biopsied in the sequential blastocyst hatching and biopsy protocol paired with the ablation of one-fourth of the zona pellucida (ZP) were matched with 835 FETs with PGT-A cycles including only embryos biopsied in the day 3 prehatching protocol by female age (±1 year), number of embryos transferred, use of gestational carrier or egg donor, and day of blastocyst transfer. Only FETs with euploid blastocysts graded no lower than 4BB were included, and cycles with fewer than five oocytes were excluded. SR after thawing, CPR, ongoing IR, and LBR were significantly higher in the FET cycles with the embryos biopsied in the sequential hatching and biopsy protocol. Four cases of monozygotic twin pregnancies were reported with the day 3 prehatching protocol and none with the sequential hatching and biopsy protocol., Conclusion(s): Our results show, for the first time, that using different blastocyst biopsy protocols can affect clinical outcomes. Because the study was retrospective, our findings should be validated in a prospective trial., (Copyright © 2019 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Research Question: Does complete mechanical removal of the zona pellucida modify the outcome of transfer of vitrified-warmed human blastocysts?, Design: In a prospective randomized controlled study, 419 couples were allocated to either zona pellucida-free (n = 209) or zona intact (n = 210) vitrified-warmed embryo transfer. Main outcome measures included clinical pregnancy, implantation and ongoing pregnancy rates., Results: Transfer of zona pellucida-free blastocysts resulted in clinical pregnancy, implantation and ongoing pregnancy rates (35,9%, 33,9% and 32,1%, respectively), similar to those achieved with zona intact control embryos (39%, 36,4% and 33,1%, respectively)., Conclusion: Total mechanical removal of the zona pellucida did not affect the tested parameters of clinical outcomes., (Copyright © 2019. Published by Elsevier Ltd.)

Objective: Assisted hatching (AH) was introduced 3 decades ago as an adjunct method to in vitro fertilization (IVF) and embryo transfer (ET) to improve embryo implantation rate. Limited data are available on the effect of AH on live birth rate (LBR) in advanced maternal age. The objective of this study is to investigate the effect of AH on LBR in women aged 40 years and older., Materials and Methods: A retrospective study conducted at a single academic reproductive center. Women aged ≥40 years, who were undergoing their first IVF cycle were included. Laser-assisted hatching was the method used for AH and single or double embryos were transferred. Embryo transfer was performed at the cleavage or blastocyst stage. Separate analysis was performed on each ET stage. Live birth rate was the primary outcome., Results: A total of 892 patients were included. Of these, 681 women underwent cleavage ET and 211 underwent blastocyst ET. The clinical pregnancy rate in the entire group was 15.3% and the LBR was 10.2%. Baseline and cycle parameters between the AH group and the control group were comparable. Assisted hatching in the cleavage stage was associated with lower clinical pregnancy rate (odds ratio [OR], 0.52; confidence interval [CI], 0.31-0.86; P = .012) and lower LBR (OR, 0.36; CI, 0.19-0.68; P = .001). Assisted hatching did not have any effect on outcomes in blastocyst ET., Conclusion: Assisted hatching does not improve the reproductive outcomes in advanced maternal age. Performing routine AH for the sole indication of advanced maternal age is not clinically justified.

Objective: To assess the effect of assisted hatching (AH) on live-birth rates in a retrospective cohort of patients undergoing first-cycle, autologous frozen embryo transfer (FET)., Design: Longitudinal cohort using cycles reported to the Society for Assisted Reproductive Technology Clinic Outcomes Reporting System between 2004 and 2013., Setting: Not applicable., Patient(s): Women who underwent first-cycle, autologous FET with (n = 70,738) and without (n = 80,795) AH reported from 2004 to 2013., Intervention(s): None., Main Outcome Measure(s): Live births., Result(s): Propensity matching was used to account for confounding covariates, and a logistic regression model was constructed to identify the predictors of live-birth rates in relationship to AH. In all first-cycle FETs, there was a slight but statistically significant decrease in the live-birth rate with AH compared with no AH (34.2% vs. 35.4%). In older patients and in the years 2012-2013 AH was associated with decreased live births. Live-birth rates and the number of AH cycles performed before FET vary by the geographic location of clinics., Conclusion(s): Assisted hatching slightly decreases the live-birth rate in first-cycle, autologous FET. Its use should be carefully considered, especially in patients 38 years old and older. Prospective, clinical studies are needed to improve our knowledge of the impact of AH., (Copyright © 2017 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Objective: To assess perinatal risk of major congenital anomalies in children born after embryo transfer with assisted hatching (AH)., Design: Retrospective cohort study., Setting: Not applicable., Patient(s): Cycles registered from 2010 to 2012 and conceived via single-embryo transfer were included for the analysis. Live births, still births after 22 weeks of gestation, and selectively terminated cases because of congenital anomalies were included., Intervention(s): None., Main Outcome Measure(s): Major congenital anomaly., Result(s): AH was performed in 35,488 cycles among 72,125 included cycles (49.2%). A total of 1,046 major congenital anomalies (1.4%) were identified (1.36% in AH group vs. 1.50% in non-AH group). Overall risks for major congenital anomalies were not significantly different between AH and non-AH groups adjusting for maternal age, calendar year, fetal sex, embryo stage at transfer, and status of cryopreservation. There were 1,009 cases of twins (1.5%) and 10 cases of triplets (0.015%) among all included cycles. No specific organ system demonstrated significant association between AH and non-AH groups. Subgroup analysis demonstrated no significant association between AH and non-AH groups in intracytoplasmic sperm injection cycles or in vitro fertilization in fresh cycles. Similar nonsignificant association was observed between early-cleavage or blastocyst stage at transfer in frozen-thawed cycles., Conclusion(s): Our results suggest that AH alone does not increase the risk of major congenital anomaly., (Copyright © 2015 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Aim: The aim of this study was to assess the efficacy of assisted hatching (AH) in assisted reproductive technology (ART) treatment., Material and Methods: In this retrospective observational study, the data of patients who were registered in the National ART Registry System of Japan between January and December 2010 were analyzed. The descriptive statistics and validity of AH in fresh embryo transfer (ET) and frozen-thawed ET were assessed by using multiple logistic regression analyses., Results: From a total of 105,450 single ET, 46,029 (43.7%) cycles underwent AH. A total of 9737 (21.3%) and 36,292 (60.9%) cycles underwent AH from 45,818 fresh single ET and 59,632 frozen-thawed single ET, respectively. In the fresh ET patients that underwent AH, the clinical pregnancy and live birth rate were significantly decreased in patients of all ages compared with that of the non-AH group. In the frozen-thawed ET patients, there was no significant difference in pregnancy and live birth rate between the AH group and the non-AH group., Conclusion: AH treatment was more frequently performed in frozen-thawed ET patients than in fresh ET patients, and in the blastocyst stage than in the early cleavage stage. A significantly decreased pregnancy and live birth rate was observed in the fresh ET patients who underwent AH. In the frozen-thawed ET patients who underwent AH, improvement in the clinical pregnancy and live birth rate was not observed. Further studies on the indication and application of AH in ART treatment are required., (© 2014 The Authors. Journal of Obstetrics and Gynaecology Research © 2014 Japan Society of Obstetrics and Gynecology.)

Objective: To evaluate factors associated with monozygosity (MZ) (number of fetal heartbeats on early ultrasound greater than the number of embryos transferred) and the risk of recurrence in subsequent pregnancies using a national assisted reproduction database., Design: Historical cohort study., Setting: Clinic-based data., Patient(s): 197,327 pregnancies (including 2,824 with evidence of MZ) from cycles reported to the Society for Assisted Reproductive Technology Clinic Outcome Reporting System (SART CORS) between 2004 and 2010., Intervention(s): None., Main Outcome Measure(s): Evidence of MZ, adjusted odds ratios and their 95% confidence intervals computed from logistic regression models., Result(s): In the univariate analysis, the risk of MZ was increased with ovulation disorders, donor oocytes, gonadotropin-releasing hormone agonist (GnRH-a) suppression, assisted hatching (AZH), and day 5-6 transfer, and was decreased with higher follicle-stimulating hormone (FSH) doses (≥3,000 IU). In the multivariate analysis, the risk of MZ was increased with GnRH-a suppression, AZH, and decreased with intracytoplasmic sperm injection (ICSI) and higher FSH dose. The interaction showed that although MZ was more likely with day 5-6 embryos, AZH had a minimal nonsignificant effect, whereas in day 2-3 embryos, AZH had a substantial statistically significant effect. Only one woman had a recurrence of MZ in a subsequent assisted reproduction pregnancy, which is consistent with randomness., Conclusion(s): The risk of MZ was higher with fresh day 5-6 embryos, donor oocytes, GnRH-a suppression, lower FSH doses, and AZH (particularly with day 2-3 embryos)., (Copyright © 2014 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

To evaluate whether laser-mediated assisted hatching (AH) performed on vitrified/warmed blastocysts before embryo transfer can improve live birth rate. The "pArtiaL zonA pelluciDa removal by assisteD hatchINg of blastocysts (ALADDIN)" is a 2-center comparative study with a parallel randomized controlled design. University hospital. Participants were recruited between September 2018 and November 2021. They were aged 18–39 years, underwent nondonor in vitro fertilization cycles, and were scheduled for elective single embryo transfer with vitrified/warmed blastocysts. Those with uterine abnormalities, body mass index of >35 kg/m2, severe male factor infertility, or performing preimplantation genetic testing were excluded. Assisted hatching was performed using a 1,480 nm diode laser, removing approximately one-third of the zona pellucida with continuous 0.2 ms pulses applied from the 1–5 o'clock positions. The primary outcome was the live birth rate. Secondary end points included clinical pregnancy, miscarriage, multiple pregnancies, preterm births, obstetric and neonatal complications, and congenital anomalies. Overall, 698 participants met the inclusion criteria and were randomized: 352 patients were assigned to the AH arm and 346 to the control arm. Of the participants, 105 (29.8%) and 101 (29.2%), respectively, achieved a live birth after treatment. The relative risk of live birth in patients with vitrified/warmed blastocysts treated with AH was 1.02 (95% confidence interval, 0.86–1.19). Exploratory subgroup analyses for women's age, recruiting centers, indications for in vitro fertilization, method of insemination, blastocyst quality, and days of blastocyst development failed to highlight any clinical situation that could benefit from AH in thawed blastocysts. In patients undergoing frozen embryo transfer with vitrified/warmed blastocysts, laser AH does not improve the live birth rate. Further studies are required to rule out milder but potentially interesting benefits in specific subgroups of patients. ClinicalTrials.gov: NCT03623659. [ABSTRACT FROM AUTHOR]

The mammalian zygote, formed after a sperm fertilizes an egg, undergoes several rounds of mitosis and morphogenesis to form the blastocyst. During the peri-implantation period, the blastocyst hatches out of the zona pellucida (ZP) and invades the receptive uterine endometrium. This process promotes maternal-fetal dialogue at the physiological and molecular level, thereby initiating the implantation process. Blastocyst hatching is a consequence of elevated osmotic pressure due to active Na+/K+ ion transporter in the blastocyst cavity, as well as proteases produced by trophectoderm (TE) that hydrolyze the ZP. This review summarizes the process underpinning blastocyst hatching, such as the hatching schedule, the location of TEs during initial hatching out of the ZP, the molecules involved in blastocyst hatching, and how these processes affect implantation events. Additionally, we focus on identifying crucial molecules that may influence the quality of implantation and predict the outcome of embryo implantation. Further understanding the mechanism of these molecules may help us to improve the efficiency of Assisted reproductive technology (ART) in livestock breeding. This review provides insight into embryonic development, specifically during the short-term process of blastocyst hatching and its effects on the following implantation. • Blastocyst hatching is affected by multiple factors and critical for successful embryo implantation. • Hatching process affects the developmental potential of blastocysts and pregnancy outcomes. • Assisted hatching may improve the efficiency of embryo transfer in livestock. [ABSTRACT FROM AUTHOR]

At present, there is no standardised protocol for assisted hatching (AH) and the field is beset with contradictory data. We hypothesised that such contradiction may be related to inconsistencies in clinical practice. This study aimed to investigate the application, preferences, and variations of AH in current clinical practice prior to embryo transfer (AHpET) and biopsy (AHpBP). An online voluntary survey, consisted of 25 questions regarding different aspects of AH, was circulated amongst different fertility centres via newsletters between October 2019 and March 2020. One-hundred twenty-nine different fertility centres participated in the survey. AHpBP was widely used (90.6% [48/53]) amongst these centres, especially for trophectoderm biopsy (92.2% [47/51]). In contrast, only 64.6% (73/113) of centres administrated AHpET; the application of AHpET was even lower in UK-based centres (36.6% [15/41]). Although laser pulses have become the predominant technique for AH, significant variation existed in the precise strategy. Zona pellucida (ZP) drilling was the main method for AHpBP, whilst both ZP drilling and ZP thinning were applied equally for AHpET. Furthermore, the ZP manipulation varied widely with regards to the size of the ZP opening and the extension of ZP thinning. This is the first representative survey relating to the current practice of AH. Laser-assisted AH is used extensively, especially for AHpBP. However, there is significant disparity in clinical practice across different centres. Future research should aim to create a standardised protocol for AH to help reduce the evident variation in clinical practice and investigate the true value of AH. [ABSTRACT FROM AUTHOR]

Purpose: To ascertain if assisted hatching (AH) increases the risk of placenta-associated diseases and perinatal outcomes after frozen–thawed cleavage-stage embryo transfer. Methods: We retrospectively evaluated 924 women who conceived with frozen–thawed cleavage-stage embryos transfer with (n = 390) or without (n = 534) laser-AH between 2013 and 2015. Data were obtained from the database on in vitro fertilization (IVF) patients in Shanghai First Maternity and Infant Hospital. We assessed neonatal (preterm birth, low birthweight, fetal macrosomia, stillbirth) and obstetric (miscarriage, ectopic pregnancy, post-term pregnancy, gestational diabetes (GDM), preeclampsia, intrahepatic cholestasis (ICP), placenta previa, placental abruption, premature rupture of membranes) outcomes. Results: In twins, the median birthweight was lower in the AH group than that in the control group, and the prevalence of low birthweight (< 2500 g) was significantly higher in the AH group; after adjusting for maternal age, body mass index, mode of fertilization, and parity, no significant difference was found. In twins, no significant difference was detected in the prevalence of stillbirth or preterm pregnancy. In singleton births, there was no significant difference in the prevalence of low birthweight, macrosomia, preterm pregnancy or post-term pregnancy between the two groups. In singletons and twins, there were no significant differences in the prevalence of miscarriage, ectopic pregnancy, preeclampsia, GDM, ICP, or placenta abruption between the two groups. Conclusions: AH is a relatively safe method and our study provides important information for using this method in carefully selected patients. [ABSTRACT FROM AUTHOR]

For in vitro produced embryos generated from in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) procedure, the intra- and extra-environmental factors during in vitro culture have significant impact on latter embryo development and fetus growth. Assisted hatching (AH), an effective approach to facilitate hatchability for in vitro generated embryos, is an essential step for successful embryo implantation in the uterus. However, regarding the different AH methods reported in clinical practice, it is still unknown whether zona pellucida (ZP) broken is based on AH applied in diverse stages of embryos affect implantation and fetal development. Here, piezo-mediated AH treatments were classified into four categories: (1) drilling one small hole (SH) with a diameter of 10 μm on ZP (SH); (2) drilling one large hole (LH) with a diameter of 40 μm on ZP (LH); (3) made a small area with diameter of 40-μm thinner on ZP [small area thinner (ST)]; (4) made a large area with a diameter of 80-μm thinner [large area thinner (LT)]. These four AH treatments were applied in different stage embryos including two-cell, four-cell, and morula. The most efficient AH approach was chosen according to the final hatch rate at 120 h after fertilization. We found that the approach of SH applied in morula-stage embryos obtained the highest hatch rate. To further investigate if this treatment has any side effect on later development after embryo transfer, we evaluated embryo implantation, gestational period, litter size, and growth. Our results showed that SH applied in morula-stage embryos could facilitate the implantation process and increase litter size. Meanwhile, this approach had no side effect on birth weight, growth, or gender ratio in the offspring. We conclude that drilling a SH on ZP in morula-stage embryos is an effective and reliable AH approach for in vitro cultured embryos in rodent. And this approach is worth further investigating in human-assisted reproductive technology.

Study Question: What is the prevalence of multiple pregnancy with zygotic splitting after single embryo transfer (SET)?Summary Answer: The prevalence of multiple pregnancy with zygotic splitting after SET was 1.36%.What Is Known Already: In 2008, the Japan Society of Obstetrics and Gynaecology (JSOG) recommended the adoption of SET to reduce multiple births. Since then, to improve the clinical pregnancy rate, elective SET using blastocyst transfer and frozen-warmed ET has increased. Blastocyst culture and zona pellucida manipulation, including ICSI and AH, have been widely reported as risk factors for monozygotic twinning. However, all these studies may have included cases with dizygotic pregnancies produced by a transferred embryo and a spontaneous conception.Study Design, Size, Duration: A retrospective observational study was performed, based on 937 848 SET cycles in registered ART data from the JSOG between 2007 and 2014. The study was approved by the Registration and Research Subcommittee of the JSOG and Juntendo University Ethics Committee.Participants/materials, Setting, Methods: To identify possible factors affecting the prevalence of zygotic splitting, we identified pregnancies, in which the number of foetuses exceeded the number of gestational sacs (GSs), to restrict our analysis to 'true' zygotic splitting. Multiple logistic regression analysis was performed using singleton pregnancy after SET, as control. P < 0.05 was considered statistically significant.Main Results and the Role Of Chance: Fresh and frozen-warmed SET produced 276 934 clinical pregnancies (29.5%/SET), including 4310 twins (1.56% of pregnancies) and 109 triplets (0.04% of pregnancies). Based on sex analysis of dichorionic twins after SET, the prevalence of multiple pregnancy with zygotic splitting was 1.36%. Statistical analysis revealed that compared to singleton pregnancies zygotic splitting pregnancies were associated with frozen-warmed ET cycles (odds ratio [OR] = 1.34; 95% CI: 1.16-1.55), blastocyst culture (OR = 1.79; 95% CI: 1.54-2.09) or AH (OR = 1.21; 95% CI: 1.08-1.35). In fresh ET cycles, the prevalence rate of zygotic splitting pregnancy after single blastocyst transfer was significantly higher than that after SET cycles with cleavage embryos (OR = 2.20; 95% CI: 1.83-2.66). However, no significant difference in ovarian stimulation and fertilization methods was recognized.Limitations, Reasons For Caution: In the current Japanese ART registry system, data regarding frozen-warmed ET do not include information about ovarian stimulation and fertilization methods. Registration for AH only began in 2010. There is no way of validating if data submitted by clinics is correct.Wider Implications Of the Findings: Clinicians should consider whether to counsel couples about the small increase in the risk of zygotic splitting associated with some embryo manipulations.Study Funding/competing Interest(s): No external funds were used for the study. The authors have no competing interests to declare.Trial Registration Number: None. [ABSTRACT FROM AUTHOR]

Objective: To identify the incidence and risk factors associated with IVF-conceived monozygotic twinning (MZT).Design: Retrospective study.Setting: Academic hospital.Patient(s): A total of 3,463 women with clinical pregnancies between January 2014 and February 2015 were analyzed.Intervention(s): None.Main Outcome Measure(s): The measures were the incidence of MZT based on the number of embryos that were replaced, type of insemination method (conventional IVF or intracytoplasmic sperm injection [ICSI]), with or without the use of assisted hatching (AH), and day of embryo transferred in fresh and frozen cycles.Result(s): Ninety-three women (2.69%) with MZT were observed. No statistically significant differences were observed in the cycle parameters of fresh or frozen cycles between MZT and other non-MZT pregnancies. Specific IVF procedures or techniques, such as the number of embryo replaced, zona pellucida manipulation (ICSI and AH), and freeze-thaw procedure, did not significantly increase the rate of MZT, except for the day of embryo transferred. Compared with day 3 transferred, day 4 and 5/6 transferred showed an increased probability of MZT (odds ratio [OR], 2.73; 95% confidence interval [CI], 1.16-6.42 for day 4 transferred and OR, 3.68; 95% CI, 2.29-5.93 for day 5/6 transferred).Conclusion(s): Extended culture (advanced embryo stage) in fresh and frozen cycles appeared to be associated with increased rates of MZT. The effect of the number of embryos transferred, ICSI and AH, and freeze-thaw procedures on the risk for MZT was not demonstrated. [ABSTRACT FROM AUTHOR]

Zona pellucida (ZP) manipulation, termed “assisted hatching” (AH), has been introduced in order to favor embryo hatching and ultimately improve assisted reproductive technology success but with poor proofs of safety and biological plausibility. We herein provide a systematic review of clinical outcomes following the application of different methods of ZP manipulation on fresh or frozen/thawed embryos at different developmental stages in different groups of patients. Out of the 69 papers that compared the clinical outcomes deriving from hatched versus non-hatched embryos, only 11 considered blastocysts while the rest referred to cleavage stage embryos. The ZP thinning of fresh embryos either by chemical or laser approach was shown to provide very limited benefit in terms of clinical outcomes. Better results were observed with procedures implying a higher degree of zona manipulation, including zona removal. Studies comparing the mechanical or chemical procedures to those laser-mediated consistently reported a superiority of the latter ones over the former. Literature is consistent for a benefit of ZP breaching in thawed blastocysts. This review provides the current knowledge on the AH procedure in order to improve its efficacy in the appropriate context. Embryologists might benefit from the approaches presented herein in order to improve Assisted Reproduction Technologies (ART) outcomes. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to determine if zona pellucida thickness variation (ZPTV) is associated with implantation and if this relationship changes with use of assisted hatching (AH). Methods: Day 3 embryos from single or double embryo transfers (DETs) performed between 2014 and 2016 were included. ZPTV was assessed by examining photographs taken before transfer using an automated image processing platform to segment the zona pellucida (ZP) with an active contour technique. One hundred points were obtained of ZP thickness (ZPT) of each embryo to calculate ZPTV ([maximum ZPT-mean ZPT]/mean ZPT). Logistic regression was used to calculate the odds ratio (OR) and 95% confidence intervals (CI) of implantation by tertile of ZPTV. Maternal age and AH were adjusted for a priori . Other cycle and embryo characteristics were adjusted for if they altered the continuous effect estimate by >10%. Results: There was no statistically significant association between ZPTV and implantation across tertiles although embryos with greater ZPTV showed a trend of decreased implantation (Tertile 2 (T2) versus Tertile 1 (T1), OR = 0.80, CI = 0.50-1.28; Tertile 3 (T3) versus Tertile 1 (T3), OR = 0.75, CI = 0.47-1.20). While similar nonsignificant trends for the association between ZPTV and implantation were observed across tertiles after stratification of embryos hatched or not, embryos with the greatest ZPTV had slightly higher odds for implantation when AH was utilized (T3 vs. T1: with AH, OR = 0.89, CI = 0.49-1.62; without AH, OR = 0.61, 0.29-1.27). Conclusion: ZPTV was not associated with implantation after day 3 transfer. This finding did not vary by use of AH. [ABSTRACT FROM AUTHOR]

Infertility, defined as the inability to conceive within 1 year of unprotected intercourse, affects an estimated 80 million individuals worldwide, or 10-15% of couples of reproductive age. Assisted reproductive technology includes all infertility treatments to achieve conception; in vitro fertilization is the process by which an oocyte is fertilized by semen outside the body; non-in vitro fertilization assisted reproductive technology treatments include ovulation induction, artificial insemination, and intrauterine insemination. Use of assisted reproductive technology has risen steadily in the United States during the past 2 decades due to several reasons, including childbearing at older maternal ages and increasing insurance coverage. The number of in vitro fertilization cycles in the United States has nearly doubled from 2000 through 2013 and currently 1.7% of all live births in the United States are the result of this technology. Since the birth of the first child from in vitro fertilization >35 years ago, >5 million babies have been born from in vitro fertilization, half within the past 6 years. It is estimated that 1% of singletons, 19% of twins, and 25% of triplet or higher multiples are due to in vitro fertilization, and 4%, 21%, and 52%, respectively, are due to non-in vitro fertilization assisted reproductive technology. Higher plurality at birth results in a >10-fold increase in the risks for prematurity and low birthweight in twins vs singletons (adjusted odds ratio, 11.84; 95% confidence interval, 10.56-13.27 and adjusted odds ratio, 10.68; 95% confidence interval, 9.45-12.08, respectively). The use of donor oocytes is associated with increased risks for pregnancy-induced hypertension (adjusted odds ratio, 1.43; 95% confidence interval, 1.14-1.78) and prematurity (adjusted odds ratio, 1.43; 95% confidence interval, 1.11-1.83). The use of thawed embryos is associated with higher risks for pregnancy-induced hypertension (adjusted odds ratio, 1.30; 95% confidence interval, 1.08-1.57) and large-for-gestation birthweight (adjusted odds ratio, 1.74; 95% confidence interval, 1.45-2.08). Among singletons, in vitro fertilization is associated with increased risk of severe maternal morbidity compared with fertile deliveries (vaginal: adjusted odds ratio, 2.27; 95% confidence interval, 1.78-2.88; cesarean: adjusted odds ratio, 1.67; 95% confidence interval, 1.40-1.98, respectively) and subfertile deliveries (vaginal: adjusted odds ratio, 1.97; 95% confidence interval, 1.30-3.00; cesarean: adjusted odds ratio, 1.75; 95% confidence interval, 1.30-2.35, respectively). Among twins, cesarean in vitro fertilization deliveries have significantly greater severe maternal morbidity compared to cesarean fertile deliveries (adjusted odds ratio, 1.48; 95% confidence interval, 1.14-1.93). Subfertility, with or without in vitro fertilization or non-in vitro fertilization infertility treatments to achieve a pregnancy, is associated with increased risks of adverse maternal and perinatal outcomes. The major risk from in vitro fertilization treatments of multiple births (and the associated excess of perinatal morbidity) has been reduced over time, with fewer and better-quality embryos being transferred. [ABSTRACT FROM AUTHOR]

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Objective: The goal of this study was to ascertain optimal assisted hatching (AH) method in frozen embryo transfer. We compared the effect of depending on whether mechanical or laser-AH was performed before or after the vitrification of embryo development rate and blastocyst cell numbers. Methods: In order to induce superovulation, pregnant mare's serum gonadotropin followed by human chorionic gonadotropin were injected into 4- to 5-week-old female mice. 2-cell embryos were then collected by flushing out the oviducts. The Expanded blastocysts were recovered after the collected embryos were incubated for 48 hours, and were then subjected to artificial shrinkage (AS) and cross-mechanical AH (cMAH) or quarter-laser zona thinning-AH (qLZT-AH) were carried out using the expanded blastocysts before or after vitrification. After 48 hours of incubation, followed by vitrification and thawing (V-T), and blastocysts were fluorescence stained and observed. Results: The rate of formation of hatched blastocysts after 24 and 72 hours of incubation was significantly higher in the AS/qLZT-AH/V-T group than in the other groups (p<0.05). The cell number of the inner cell mass was higher in AS/V-T/non-AH and AS/V-T/cMAH groups than those of others (p<0.05). In the control group, the number of trophectoderm and the total cell number were higher than in the AS-AH group (p<0.05). Conclusion: The above results suggest that AS and AH in vitrification of expanded blastocysts lead to the more efficient formation of hatched blastocysts in mice. [ABSTRACT FROM AUTHOR]

Purpose: To assess the incidence of monozygotic twinning (MZT) among cases undergoing assisted reproductive technology (ART) treatment. Methods: We performed a retrospective observational study and analyzed the data of patients who were registered in the national ART registry system of Japan from January to December 2010; only the data of patients with single embryo transfer (ET) were included. Results: Of 30,405 pregnancies, 425 resulted in MZT following fresh and frozenthawed ET. The MZT incidence among women undergoing ART was 1.4 %. Multiple logistic regression analysis indicated that cases undergoing fresh and frozen-thawed ET, blastocyst transfer had a significantly increased MZT rate ( P < 0.01). Assisted hatching (AH) and frozen-thawed ET and maternal age did not significantly affect the MZT incidence. Of 8510 fresh ET pregnancies, 104 resulted in MZT. Multiple logistic regression analysis indicated that blastocyst transfer significantly increased the MZT rate in cases undergoing fresh ET. Ovarian stimulation, intracytoplasmic sperm injection, AH, and maternal age did not significantly affect the MZT incidence. Conclusions: Blastocyst transfer was associated with an increased MZT incidence. We have to be aware of the potential risk of MZT caused by blastocyst transfer. However, further studies are required to assess the correlation among specific AH types, embryo culture conditions, and MZT incidence. [ABSTRACT FROM AUTHOR]

There are limited data on the use of steroids and antibiotics in assisted reproductive technology (ART). Our aim was to evaluate the impact of these treatments on the outcome of IVF cycles in which Assisted Hatching (AH) was performed. We studied a retrospective cohort in a large university-affiliated infertility centre. Data from 1126 AH cycles performed between 2007 and 2009 were reviewed. Cycles were categorized as 'treatment' (n = 640) and 'no treatment' (n = 486), depending on whether they received steroids and antibiotics. The primary outcome was live birth. Secondary outcomes included implantation, spontaneous abortion, biochemical, clinical and ectopic pregnancy. Logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI). OR were adjusted (AOR) for age, BMI, baseline FSH, peak estradiol, cycle number, number of oocytes retrieved, number of embryos that underwent AH, number of high-implantation potential embryos, number of embryos transferred and physician in charge. The AOR (95% CI) of live birth was 1.91 (1.08-3.38), of clinical pregnancy, 1.75 (1.08-2.83) and of biochemical pregnancy, 0.24 (0.07-0.85). Our study suggests that treatment with steroids and antibiotics during AH cycles significantly increases the odds of live birth. [ABSTRACT FROM AUTHOR]

BACKGROUND Assisted hatching (AH) is a manipulation of zona pellucida aiming to facilitate embryo implantation. METHODS Systematic review and meta-analysis of medical literature was used to evaluate the effect of AH on assisted reproduction outcomes: clinical pregnancy, live birth, multiple pregnancy and miscarriage. Additional analysis was performed in these subgroups: (i) fresh embryos transferred to unselected or non-poor prognosis women; (ii) fresh embryos transferred to women with previous repeated failure; (iii) fresh embryos transferred to women of advanced age; (iv) frozen-thawed embryos transferred to unselected or non-poor prognosis women. Analyses were based on risk ratio and 95% confidence intervals (RR, 95% CIs) using Mantel–Haenszel random effects model. RESULTS There were 28 studies (5507 participants) included. AH was related to a trend toward increased clinical pregnancy for all participants (RR = 1.11, 95% CI = 1.00–1.24), with a significant increase in subgroups 2 (RR = 1.73; 95% CI = 1.37–2.17) and 4 (RR = 1.36; 95% CI = 1.08–1.72, P< 0.01), but not for subgroups 1 and 3. For multiple pregnancy, a significant increase was observed for all participants (RR = 1.45; 95% CI = 1.11–1.90) and for subgroups 2 (RR = 2.53; 95% CI = 1.23–5.21) and 4 (RR = 3.40; 95% CI = 1.93–6.01). No significant heterogeneity was observed in subgroup analysis. CONCLUSIONS AH was related to increased clinical pregnancy and multiple pregnancy rates in women with previous repeated failure or frozen-thawed embryos. However, AH is unlikely to increase clinical pregnancy rates when performed in fresh embryos transferred to unselected or non-poor prognosis women or to women of advanced age. Due to the small sample evaluated by the pool of included studies, no proper conclusions could be drawn regarding miscarriage or live birth. [ABSTRACT FROM AUTHOR]

The World Health Organization estimates that one in six couples experience some delay in conception and an increasing number require treatment by the assisted conception (AC) procedures of in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI).The implantation rate of embryos resulting from in vitro fertilization cycles is generally less than 20%. The exposure of oocytes and embryos to the artificial conditions of in vitro culture may have negative effects on the embryo's ability to undergo normal hatching, resulting in low rates of implantation following IVF and embryo transfer. Human embryos resulting from superovulation develop more slowly in vitro compared to embryos in vivo, manifest a relatively high degree of cytogenetic abnormalities and undergo cellular fragmentation. Artificially disrupting the zona pellucida is known as assisted hatching (AH) and there is some evidence that embryos that have undergone zona manipulation for assisted hatching tend to implant one day earlier than unhatched embryos. A variety of techniques have since been employed to assist embryo hatching, including partial mechanical zona dissection, zona drilling and zona thinning, making use of acid tyrodes, proteinases, piezon vibrator manipulators and lasers. This review will consider the impact of IVF conditions on zona pellucida physiology, zona hardening, different techniques of assisted hatching, who may benefit from assisted hatching and potential hazards. [ABSTRACT FROM AUTHOR]

Objective: To report on a patient with a quintuplet pregnancy consisting of a monochorionic triamnionic triplet pregnancy and one case of monoamniotic twins after intracytoplasmic sperm injection (ICSI), laser-assisted hatching, and day 4 embryo transfer. Case Report: A 34-year-old woman who underwent ICSI due to male infertility. She underwent standard controlled ovarian hyperstimulation. Retrieved oocytes were fertilized in vitro, and 3 embryos were transferred on day 4 after laser-assisted hatching. Transvaginal ultrasound revealed a monoamniotic twin pregnancy and a monochorionic-triamniotic triplet pregnancy. A second ultrasound, 1 week later, showed three distinct foci of cardiac motion in one sac, while the sac of the monoamniotic twins had one embryo with heart beat. After extensive counseling with perinatologists about pregnancy complications, the patient elected to performed fetal reduction on the third sac. A healthy male infant was delivered by Caesarean section at 38 weeks of gestation. Conclusions: The exact mechanism of monozygotic multiple gestation is still poorly characterized. Procedures that modify the zona pellucida (e.g. ICSI and assisted embryo hatching) have been suggested as important in the monozygotic multiple gestation hypothesis, yet a definitive relationship between any clinical intervention during in vitro fertilization and the subsequent development of multiple monozygotic gestation remains speculative. Copyright © 2009 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Objective: Despite technical progress in In Vitro Fertilisation (IVF) procedure, embryo implantation rate remains low. Assisted hatching has been proposed to facilitate natural embryo hatching and implantation. Patients and methods: Our study has evaluated whether laser assisted hatching improves implantation, pregnancy and live birth rates in different cases. We studied retrospectively 143 IVF cycles concerning more than 38 years old women, 166 IVF cycles after two previous implantation failures and 180 frozen-thawed embryo transfers. Results: Population characteristics were comparable in hatched and control groups. Implantation, pregnancy and live birth rates in women more than 38 years old were comparable with or without assisted hatching. Concerning repeated implantation failures, even if implantation, pregnancy and live birth rates were higher in assisted hatching group (FIV or ICSI), the differences were not significant. After frozen-thawed embryo transfers, implantation rate was significantly better with assisted hatching (19.14% vs 8.84% [p =0.02]). Discussion and conclusion: Assisted hatching improves embryo implantation rate after frozen-thawed embryo transfer. [Copyright &y& Elsevier]

Background/Aims: Some embryo implantation problems in patients with recurrent implantation failure may be explained by the inability of the embryo to hatch out of its zona pellucida. In this case-control study, a study group which had received modified quarter laser-assisted zona thinning (mQLAZT) was compared with a control group which had not received mQLAZT with respect to reproductive outcome. Methods: Cycles from patients with a 4th fresh embryo transfer (ET) after 3 previously failed ET cycles (no β-hCG detected) were included. Cases (group A, n = 53) included ET cycles from patients who received a 4th ET with fresh embryos after mQLAZT. Controls (group B, n = 86) included ET cycles from patients who had a 4th ET without mQLAZT. The clinical implantation rate and live birth rate per embryo transferred were measured. Results: The clinical implantation rate with positive fetal heart beat per embryo transferred was significantly higher (p = 0.035) in group A (22/107 or 21%) than in group B (18/166 or 11%). Conclusion: The data of this case-control study suggest that mQLAZT can be effective in the treatment of patients with recurrent implantation failure, but need to be confirmed by randomized trials. Copyright © 2008 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The aim of this study was to determine if assisted hatching (AH) could improve the rates of pregnancy and implantation for both fresh and frozen-thawed embryo transfer cycles. A total of 760 fresh embryo transfer cycles and 200 frozen-thawed embryo transfer cycles were randomly assigned to either the treatment group (AH) or the control group (no AH). Zona thinning by laser was performed just before embryo transfer. In fresh embryo transfer cycles, the AH group and control group results were comparable. There were no significant differences in the rates of positive human chorionic gonadotrophin (HCG; 47.5 versus 48.8%), clinical pregnancy (42.4 versus 42.6%), or implantation (26.3 versus 25.2%) between the two groups. However, in frozen-thawed embryo transfer cycles, the rates of positive HCG (32.0 versus 17.0%), clinical pregnancy (25.0 versus 14.0%) and implantation (16.7 versus 7.3%) were significantly greater in the AH group than in the control group (P < 0.05). The results of this investigation show that in the fresh embryo transfer cycles, laser-assisted hatching by zona thinning has no impact on the rates of positive HCG, clinical pregnancy and implantation, whereas in frozen-thawed cycles, assisted hatching by zona thinning significantly increases all three of these rates. [ABSTRACT FROM AUTHOR]

Purpose To compare effectiveness of two different chemical zona thinning techniques. Method We studied 163 patients who had experienced IVF or ICSI failures in two or more cycles. Patients were assigned to one of three groups: zona intact (n=72), partial thinning (n=59), or circumferential thinning (n=73). Before transfer, the zonae pellucidae of embryos were thinned partially or circumferentially using acidified Tyrode's solution. Results Implantation rates were 8.9% in the intact zona group, 17.6% in the partial thinning group, and 11.9% in the circumferential thinning group: respective clinical pregnancy rates were 16.7% (12/72), 32.2% (19/59), and 27.4% (20/73). Both rates were significantly higher in the partial thinning group than the intact zona group. For circumferential thinning versus zona intact groups, differences fell short of significance. Conclusions Following embryo transfer failure, partial thinning would be recommended over circumferential thinning for successful assisted hatching. [ABSTRACT FROM AUTHOR]

Objective: To evaluate whether assisted hatching improves clinical outcomes of embryo transfers to good prognosis patients, defined as patients ≤39 years with normal follicle-stimulating hormone (FSH) and E2 levels, no more than one previous unsuccessful cycle of in vitro fertilization (IVF)–embryo transfer, and good embryo quality. Design: Prospective randomized controlled trial. Setting: Private assisted reproductive technology (ART) center. Patient(s): One hundred ninety-nine good prognosis patients undergoing IVF–embryo transfer. Intervention(s): In vitro fertilization followed by embryo transfer on day 3 after oocyte retrieval with or without assisted hatching using a 1,480-nm wavelength infrared laser. Main Outcome Measure(s): Clinical intrauterine pregnancy, spontaneous pregnancy loss, and live birth. Result(s): Rates of clinical intrauterine pregnancy with fetal cardiac activity (53% vs. 54% per cycle), spontaneous pregnancy loss (13% vs. 16% per pregnancy), and live birth (47% vs. 46% per cycle) were very similar between treatment cycles with laser-assisted hatching and control cycles in which embryos were transferred without assisted hatching. There were no significant differences between treatment and control groups in any measured clinical outcome parameters. Conclusion(s): Assisted hatching does not improve clinical outcomes among good prognosis patients. [Copyright &y& Elsevier]

Single embryo transfer is becoming increasingly popular in IVF/ICSI. More IVF/ICSI cycles therefore include freezing of high quality embryos, and the cumulative effect of such cycles becomes more important. To improve the results obtained using frozen thawed embryos, the predictive value of embryo and patient characteristics was analysed retrospectively. Excess embryos were frozen on day 2 according to routine procedures and thawed 24 h before transfer. The women were either treated with oestradiol/progesterone, or the transfer took place after a natural cycle. Of 1777 embryos thawed, 1360 survived (survival rate 76.5%). In the 410 transfer cycles, 819 embryos were transferred, giving 109 positive serum HCG tests and 69 clinical pregnancies. The implantation rate was 10.4%. Five parameters were positively related to implantation: (i) four or more cells at the freezing time (day 2): (ii) resumption of mitosis after thawing; (iii) more than six cells at transfer (day 3); (iv) assisted hatching and (v) child in a previous fresh cycle. The relative predictive value of these parameters may be a guideline for the selection of embryos used for transfer. Assisted hatching may become routine in freeze-thaw cycles if its utility is confirmed in subsequent studies. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effect of degenerated (lysed) blastomere removal on implantation and pregnancy rates in cleavage-stage cryo–embryo transfer (ET) cycles. Design: Randomized clinical trial. Setting: Private reproductive medical center. Patient(s): A total of 88 patients who received frozen–thawed ET, divided into two groups. Intervention(s): Embryo freezing and thawing; opening of the zona pellucida and removal of cryodamaged blastomeres (in the study group), followed by same-day ET. Main Outcome Measure(s): Extent of survival of cleavage-stage embryos after the freeze–thaw procedure; embryo implantation and clinical pregnancies. Result(s): Oocyte number per patient, fertilization rate, embryo development rate (and quality), and freezing rates were similar in the two groups in the fresh cycle. In the control group, a total of 55 embryos (25%) of the 217 thawed remained fully intact, and 53 (26%) of the 207 in the study group remained intact. The average number of embryos transferred per group was similar (control, 3.4 ± 0.9; study, 3.3 ± 0.9). Implantation rates were 12% and 26% in the control and study groups, respectively. The clinical pregnancy rate was 23% in the control group and 64% in the study group when lysed cell removal was performed. Conclusion(s): The results show that pregnancy and implantation rates are higher in the study group; therefore, the removal of degenerated blastomeres may be beneficial to all patients who undergo cleavage-stage, frozen–thawed ET. [Copyright &y& Elsevier]

Monochorionic triplet pregnancies are very rare. Here we report 2 cases of multiple pregnancies with monochorionic triplets following intracytoplasmic sperm injection (ICSI) and day 3 embryo transfer. The 2 women concomitantly underwent controlled ovarian hyperstimulation due to male factor infertility. Following oocyte retrieval, ICSI and assisted hatching (AH) were performed, and the 2 women conceived consecutively. One patient had a quadruplet pregnancy, which included monochorionic triplets, while the other had monochorionic triplets. Selective embryo reduction by intracardiac KCl injection targeted at 2 of the triplets was performed on the patient with the quadruplet pregnancy, but the third triplet also died. The gestation continued as a singleton pregnancy, and the patient gave birth to a healthy female baby at 38 weeks. The other patient gave birth to 3 healthy female babies at 34 weeks. Possible etiologic factors for the formation of monozygotic splitting among women undergoing assisted reproduction treatment are discussed. [ABSTRACT FROM AUTHOR]

This follow-up study of children born after laser assisted hatching (LAH) with a non-contact laser aims to compile data on karyotypes, deliveries, congenital malformations and growth parameters to evaluate the safety of this new technique. The study design consisted of karyotyping and completion of a standardized questionnaire. Data were analyzed for the first 134 children born after LAH.Indication for LAH were the age (over 35 years) (group I), previously minimum three unsuccessful IVF-ET treatment cycles (group II) and age >35 years with at least three unsuccessful IVF cycles (group III).In our study group of 134 babies we found no increase in the major congenital malformation rate (2.2%) which is comparable with the major congenital malformation rate (3%) among all deliveries at our hospital. No increase in chromosomal aberrations could be observed. Neither could we observe a difference in minor congenital malformations between the LAH treated group and all deliveries at our hospital (10.4% versus 11.1%).On this limited number of children born after LAH there was neither evidence of an increased incidence of chromosomal aberrations nor of congenital malformations. [Copyright &y& Elsevier]

: ObjectiveTo compare cycle outcomes in similar populations of women over 40 who underwent blastocyst transfer compared with women who had day 3 embryo transfer with assisted hatching (ET/AH).: DesignRetrospective study: SettingUniversity hospital–based program.: Patient(s)Eighty-six IVF cycles in women ages 40 to 43 years who had more than three eight-cell embryos on day 3.: Intervention(s)On day 3 of embryo culture, patients chose either to undergo blastocyst transfer or day 3 ET/AH.: Main outcome measure(s)Pregnancy and cryopreservation rates were recorded.: Result(s)In 48 cycles, blastocyst transfer was performed, and in 38 cycles day 3 ET/AH was performed. There was no statistically significant difference between the blastocyst transfer group and the day 3 ET/AH group with respect to age (41.1 ± 0.9 years vs. 41.6 ± 0.8 years), percentage of intracytoplasmic sperm injection cycles (29.2% vs. and 27.6%), number of oocytes (14.9 ± 5.6 vs. 12.8 ± 4.0), or number of eight-cell embryos (6.1 ± 2.2 vs. 5.4 ± 1.5). Significantly fewers embryos were transferred per cycle with blastocyst transfer (2.6 ± 1.0) compared with day 3 ET/AH (5.9 ± 2.0). The viable pregnancy rate was similar in the blastocyst transfer group (29.2%) and in the day 3 ET/AH group (26.3%). Embryos for cryopreservation were available in significantly more cycles in the blastocyst transfer group (52.1%) than in the day 3 ET/AH group (21.1%). Cleavage stage arrest occurred only in one cycle.: Conclusion(s)Blastocyst transfer appears to be as effective as day 3 ET/AH in older patients with good embryos. Higher cryopreservation rate in the blastocyst transfer group may represent an advantage over day 3 ET/AH. Older women may also benefit from the information that extended culture provides them regarding their oocyte quality. [Copyright &y& Elsevier]

From 1993 to 1994, in our centre, laser-assisted hatching was performed on 2- to 4-cell stage embryos obtained from in-vitro fertilization (IVF) patients. We treated 376 embryos from 96 patients with repeated IVF failures (two to four attempts) (group A) and 397 embryos from 111 patients undergoing IVF for the first time (group B). Embryos were transferred immediately after the laser treatment. Both groups were compared to control groups (A' and B') whose embryos were transferred with intact zona pellucida (ZP). The resulting clinical pregnancies were 41 in A and 44 in B versus 24 in A' and 23 in B' respectively. The pregnancy rates per patient were 42.7 and 39.6% versus 23.1 and 19% in the control groups (P < or = 0.05), while the implantation rates per embryo were 12.2% in A and 11.8% in B versus 7.3% and 7.1%. These results show that laser zona thinning of human embryos at 48 h after egg retrieval significantly increases the implantation and pregnancy rate (P < or = 0.05). [ABSTRACT FROM AUTHOR]

Objective: To report a normal twin delivery after transfer of two fresh day 7 blastocysts.Design: Case report.Setting: Private infertility clinic.Patient(s): A 35-year-old woman with a 6-year history of primary infertility with significant pelvic adhesions.Intervention(s): Review of individual IVF-ET therapy cycle.Main Outcome Measure(s): Full-term delivery after day 7 blastocyst transfer.Result(s): During the patient's first IVF-ET cycle, the decision was made to undertake blastocyst transfer after extended culture. No blastocysts had formed until late on day 6, by which time the patient had been hospitalized with a renal stone. Subsequently, on day 7, the patient was asymptomatic and presented for embryo transfer, and after assisted hatching, two expanded blastocysts were transferred to her uterus under ultrasound guidance. After confirmation of implantation of a viable twin, pregnancy was uneventful with no obstetrical complications, and a dizygotic twin was delivered vaginally at 38 weeks of gestation.Conclusion(s): Few reports have been made regarding viability of more slowly developing blastocysts; however, this case indicates that blastocysts that did not fully expand until day 7 of extended in vitro culture are still able to implant after superovulation and IVF-ET therapy. Assisted hatching of these embryos may have been beneficial in achieving this successful outcome by hastening the blastocyst hatching, allowing more rapid contact with the endometrium. [ABSTRACT FROM AUTHOR]