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STUDY QUESTION Which clinical and embryological factors should be considered to apply double embryo transfer (DET) instead of elective single embryo transfer (eSET)? SUMMARY ANSWER No clinical or embryological factor per se justifies a recommendation of DET instead of eSET in IVF/ICSI. WHAT IS KNOWN ALREADY DET is correlated with a higher rate of multiple pregnancy, leading to a subsequent increase in complications for both mother and babies. These complications include preterm birth, low birthweight, and other perinatal adverse outcomes. To mitigate the risks associated with multiple pregnancy, eSET is recommended by international and national professional organizations as the preferred approach in ART. STUDY DESIGN, SIZE, DURATION The guideline was developed according to the structured methodology for development and update of ESHRE guidelines. Literature searches were performed in PUBMED/MEDLINE and Cochrane databases, and relevant papers published up to May 2023, written in English, were included. Live birth rate, cumulative live birth rate, and multiple pregnancy rate were considered as critical outcomes. PARTICIPANTS/MATERIALS, SETTING, METHODS Based on the collected evidence, recommendations were discussed until a consensus was reached within the Guideline Development Group (GDG). A stakeholder review was organized after the guideline draft was finalized. The final version was approved by the GDG and the ESHRE Executive Committee. MAIN RESULTS AND THE ROLE OF CHANCE The guideline provides 35 recommendations on the medical and non-medical risks associated with multiple pregnancies and on the clinical and embryological factors to be considered when deciding on the number of embryos to transfer. These recommendations include 25 evidence-based recommendations, of which 24 were formulated as strong recommendations and one as conditional, and 10 good practice points. Of the evidence-based recommendations, seven (28%) were supported by moderate-quality evidence. The remaining recommendations were supported by low (three recommendations; 12%), or very low-quality evidence (15 recommendations; 60%). Owing to the lack of evidence-based research, the guideline also clearly mentions recommendations for future studies. LIMITATIONS, REASONS FOR CAUTION The guideline assessed different factors one by one based on existing evidence. However, in real life, clinicians' decisions are based on several prognostic factors related to each patient's case. Furthermore, the evidence from randomized controlled trials is too scarce to formulate high-quality evidence-based recommendations. WIDER IMPLICATIONS OF THE FINDINGS The guideline provides health professionals with clear advice on best practice in the decision-making process during IVF/ICSI, based on the best evidence currently available, and recommendations on relevant information that should be communicated to patients. In addition, a list of research recommendations is provided to stimulate further studies in the field. STUDY FUNDING/COMPETING INTEREST(S) The guideline was developed and funded by ESHRE, covering expenses associated with the guideline meetings, the literature searches, and the dissemination of the guideline. The guideline group members did not receive payment. DPB declared receiving honoraria for lectures from Merck, Ferring, and Gedeon Richter. She is a member of ESHRE EXCO, and the Mediterranean Society for reproductive medicine and the president of the Croatian Society for Gynaecological Endocrinology and Reproductive Medicine. CDG is the past Chair of the ESHRE EIM Consortium and a paid deputy member of the Editorial board of Human Reproduction. IR declared receiving reimbursement from ESHRE and EDCD for attending meetings. She holds an unpaid leadership role in OBBCSSR, ECDC Sohonet, and AER. KAR-W declared receiving grants for clinical researchers and funding provision to the institution from the Swedish Cancer Society (200170F), the Senior Clinical Investigator Award, Radiumhemmets Forskningsfonder (Dnr: 201313), Stockholm County Council FoU (FoUI-953912) and Karolinska Institutet (Dnr 2020-01963), NovoNordisk, Merck and Ferring Pharmaceuticals. She received consulting fees from the Swedish Ministry of Health and Welfare. She received honoraria from Roche, Pfizer, and Organon for chairmanship and lectures. She received support from Organon for attending meetings. She participated in advisory boards for Merck, Nordic countries, and Ferring. She declared receiving time-lapse equipment and grants with payment to institution for pre-clinical research from Merck pharmaceuticals and from Ferring. SS-R received research funding from Roche Diagnostics, Organon/MSD, Theramex, and Gedeo-Richter. He received consulting fees from Organon/MSD, Ferring Pharmaceuticals, and Merck Serono. He declared receiving honoraria for lectures from Ferring Pharmaceuticals, Besins, Organon/MSD, Theramex, and Gedeon Richter. He received support for attending Gedeon Richter meetings and participated in the Data Safety Monitoring Board of the T-TRANSPORT trial. He is the Deputy of ESHRE SQART special interest group. He holds stock options in IVI Lisboa and received equipment and other services from Roche Diagnostics and Ferring Pharmaceuticals. KT declared receiving payment for honoraria for giving lectures from Merck Serono and Organon. She is member of the safety advisory board of EDQM. She holds a leadership role in the ICCBBA board of directors. ZV received reimbursement from ESHRE for attending meetings. She also received research grants from ESHRE and Juhani Aaltonen Foundation. She is the coordinator of EHSRE SQART special interest group. The other authors have no conflicts of interest to declare. DISCLAIMER This guideline represents the views of ESHRE, which were achieved after careful consideration of the scientific evidence available at the time of preparation. In the absence of scientific evidence on certain aspects, a consensus between the relevant ESHRE stakeholders has been obtained. Adherence to these clinical practice guidelines does not guarantee a successful or specific outcome, nor does it establish a standard of care. Clinical practice guidelines do not replace the need for application of clinical judgement to each individual presentation, nor variations based on locality and facility type. ESHRE makes no warranty, express or implied, regarding the clinical practice guidelines and specifically excludes any warranties of merchantability and fitness for a particular use or purpose (full disclaimer available at https://www.eshre.eu/Guidelines-and-Legal). [ABSTRACT FROM AUTHOR]

Study Question: Can risks associated with novelties in assisted reproduction technologies (ARTs) be assessed in a systematic and structured way?Summary Answer: An ART-specific risk assessment tool has been developed to assess the risks associated with the development of novelties in ART (EuroGTP II-ART).What Is Known Already: How to implement new technologies in ART is well-described in the literature. The successive steps should include testing in animal models, executing pre-clinical studies using supernumerary gametes or embryos, prospective clinical trials and finally, short- and long-term follow-up studies on the health of the offspring. A framework categorizing treatments from experimental through innovative to established according to the extent of the studies conducted has been devised. However, a systematic and standardized methodology to facilitate risk evaluation before innovations are performed in a clinical setting is lacking.Study Design, Size, Duration: The EuroGTP II-ART risk assessment tool was developed on the basis of a generic risk assessment algorithm developed for tissue and cell therapies and products (TCTPs) in the context of the project 'Good Practices for demonstrating safety and quality through recipient follow-up European Good Tissue and cells Practices II (EuroGTP II)'. For this purpose, a series of four meetings was held in which eight ART experts participated. In addition, several tests and simulations were undertaken to fine-tune the final tool.Participants/materials, Setting, Methods: The three steps comprising the EuroGTP II methodology were evaluated against its usefulness and applicability in ART. Ways to improve and adapt the methodology into ART risk assessment were agreed and implemented.Main Results and the Role Of Chance: Assessment of the novelty (Step 1), consisting of seven questions, is the same as for other TCTPs. Practical examples were included for better understanding. Identification of potential risks and consequences (Step 2), consisting of a series of risks and risk consequences to consider during risk assessment, was adapted from the generic methodology, adding more potential risks for processes involving gonadic tissues. The algorithm to score risks was also adapted, giving a specific range of highest possible risk scores. A list of strategies for risk reduction and definition of extended studies required to ensure effectiveness and safety (Step 3) was also produced by the ART experts, based on generic EuroGTP II methodology. Several explanations and examples were provided for each of the steps for better understanding within this field.Limitations, Reasons For Caution: A multidisciplinary team is needed to perform risk assessment, to interpret results and to determine risk mitigation strategies and/or next steps required to ensure the safety in the clinical use of novelties.Wider Implications Of the Findings: This is a dynamic tool whose value goes beyond assessment of risk before implementing a novel ART in clinical practice, to re-evaluate risks based on information collected during the process.Study Funding/ Competing Interest(s): This study was called EUROGTP II and was funded by the European Commission (Grant agreement number 709567). The authors declare no competing interests concerning the results of this study. [ABSTRACT FROM AUTHOR]

STUDY QUESTION To evaluate the implementation of the coding systems in medically assisted reproduction (MAR) centres in the European Union (EU). SUMMARY ANSWER Our data show that a significant number of MAR centres use the Single European Code (SEC), but it also shows certain limitations to the coding. WHAT IS KNOWN ALREADY Traceability and identification of tissue and cells used for clinical application are extremely important as it is one of the key aspects of quality and safety both for the donors and the recipients. Patients as well as tissues and cells move across the European continent and far beyond, hence a uniform coding system was very much needed. The coding of tissues and cells from human origin was already embedded in the EU directives 2004/23/EC. The use of the Single European Code (SEC) on tissues and cells was enforced in 2017 for tissues and cells distributed within the EU or exported from the EU. The SEC ensures standardization within the EU, allowing the integration of the two existing codes (ISBT-128 and Eurocode) within the SEC structure. Likewise, in the MAR field, the SEC was launched in order to ensure the traceability of reproductive tissues and cells. Gametes and embryos from partner donation as well as reproductive cells and tissues of allogeneic donation were excluded from the SEC as long as they remain in the centre of origin. STUDY DESIGN, SIZE, DURATION A cross-sectional survey aimed to gain insight into the use of SEC by MAR centres was conducted between 5 November and 15 December 2018. PARTICIPANTS/MATERIALS, SETTING, METHODS The online survey was distributed among the ESHRE members. MAIN RESULTS AND THE ROLE OF CHANCE The survey results highlight the strengths and weaknesses in the practical use of the SEC. The data from the survey showed that the SEC code is something that is known in the MAR field. Our data showed that over half of the respondents were using the SEC in their centre. On the other hand, there is also criticism about the use of SEC in MAR, especially that the added value for traceability and identification in ART is found to be rather limited. LIMITATIONS, REASONS FOR CAUTION The survey response rate was rather low (4.84%). The view of the use of SEC discussed in this paper still provides insight into the use of the SEC in several MAR centres. WIDER IMPLICATIONS OF THE FINDINGS The survey highlights some knowledge gaps concerning coding. This information can be used to develop tools to increase knowledge of the SEC. STUDY FUNDING/COMPETING INTEREST(S) There was no external funding for this study. The authors declare that they have no conflict of interest. TRIAL REGISTRATION NUMBER N/A. [ABSTRACT FROM AUTHOR]

STUDY QUESTION What is good practice in ultrasound (US), and more specifically during the different stages of transvaginal oocyte retrieval, based on evidence in the literature and expert opinion on US practice in ART? SUMMARY ANSWER This document provides good practice recommendations covering technical aspects of US-guided transvaginal oocyte retrieval (oocyte pick up: OPU) formulated by a group of experts after considering the published data, and including the preparatory stage of OPU, the actual procedure and post-procedure care. WHAT IS KNOWN ALREADY US-guided transvaginal OPU is a widely performed procedure, but standards for best practice are not available. STUDY DESIGN, SIZE, DURATION A working group (WG) collaborated on writing recommendations on the practical aspects of transvaginal OPU. A literature search for evidence of the key aspects of the procedure was carried out. Selected papers (n  = 190) relevant to the topic were analyzed by the WG. PARTICIPANTS/MATERIALS, SETTING, METHODS The WG members considered the following key points in the papers: whether US practice standards were explained; to what extent the OPU technique was described and whether complications or incidents and how to prevent such events were reported. In the end, only 108 papers could be used to support the recommendations in this document, which focused on transvaginal OPU. Laparoscopic OPU, transabdominal OPU and OPU for IVM were outside the scope of the study. MAIN RESULTS AND THE ROLE OF CHANCE There was a scarcity of studies on the actual procedural OPU technique. The document presents general recommendations for transvaginal OPU, and specific recommendations for its different stages, including prior to, during and after the procedure. Most evidence focussed on comparing different equipment (needles) and on complications and risks, including the risk of infection. For these topics, the recommendations were largely based on the results of the studies. Recommendations are provided on equipment and materials, possible risks and complications, audit and training. One of the major research gaps was training and competence. This paper has also outlined a list of research priorities (including clarification on the value or full blood count, antibiotic prophylaxis and flushing, and the need for training and proficiency). LIMITATIONS, REASONS FOR CAUTION The recommendations of this paper were mostly based on clinical expertise, as at present, only a few clinical trials have focused on the oocyte retrieval techniques, and almost all available data are observational. In addition, studies focusing on OPU were heterogeneous with significant difference in techniques used, which made drafting conclusions and recommendations based on these studies even more challenging. WIDER IMPLICATIONS OF THE FINDINGS These recommendations complement previous guidelines on the management of good laboratory practice in ART. Some useful troubleshooting/checklist recommendations are given for easy implementation in clinical practice. These recommendations aim to contribute to the standardization of a rather common procedure that is still performed with great heterogeneity. STUDY FUNDING/COMPETING INTEREST(S) The meetings of the WG were funded by ESHRE. The other authors declare that they have no conflict of interest. TRIAL REGISTRATION NUMBER NA. ESHRE Pages content is not externally peer reviewed. The manuscript has been approved by the Executive Committee of ESHRE. [ABSTRACT FROM AUTHOR]

Study Question: Which clinical and embryological factors should be considered to apply double embryo transfer (DET) instead of elective single embryo transfer (eSET)?, Summary Answer: No clinical or embryological factor per se justifies a recommendation of DET instead of eSET in IVF/ICSI., What Is Known Already: DET is correlated with a higher rate of multiple pregnancy, leading to a subsequent increase in complications for both mother and babies. These complications include preterm birth, low birthweight, and other perinatal adverse outcomes. To mitigate the risks associated with multiple pregnancy, eSET is recommended by international and national professional organizations as the preferred approach in ART., Study Design, Size, Duration: The guideline was developed according to the structured methodology for development and update of ESHRE guidelines. Literature searches were performed in PUBMED/MEDLINE and Cochrane databases, and relevant papers published up to May 2023, written in English, were included. Live birth rate, cumulative live birth rate, and multiple pregnancy rate were considered as critical outcomes., Participants/materials, Setting, Methods: Based on the collected evidence, recommendations were discussed until a consensus was reached within the Guideline Development Group (GDG). A stakeholder review was organized after the guideline draft was finalized. The final version was approved by the GDG and the ESHRE Executive Committee., Main Results and the Role of Chance: The guideline provides 35 recommendations on the medical and non-medical risks associated with multiple pregnancies and on the clinical and embryological factors to be considered when deciding on the number of embryos to transfer. These recommendations include 25 evidence-based recommendations, of which 24 were formulated as strong recommendations and one as conditional, and 10 good practice points. Of the evidence-based recommendations, seven (28%) were supported by moderate-quality evidence. The remaining recommendations were supported by low (three recommendations; 12%), or very low-quality evidence (15 recommendations; 60%). Owing to the lack of evidence-based research, the guideline also clearly mentions recommendations for future studies., Limitations, Reasons for Caution: The guideline assessed different factors one by one based on existing evidence. However, in real life, clinicians' decisions are based on several prognostic factors related to each patient's case. Furthermore, the evidence from randomized controlled trials is too scarce to formulate high-quality evidence-based recommendations., Wider Implications of the Findings: The guideline provides health professionals with clear advice on best practice in the decision-making process during IVF/ICSI, based on the best evidence currently available, and recommendations on relevant information that should be communicated to patients. In addition, a list of research recommendations is provided to stimulate further studies in the field., Study Funding/competing Interest(s): The guideline was developed and funded by ESHRE, covering expenses associated with the guideline meetings, the literature searches, and the dissemination of the guideline. The guideline group members did not receive payment. DPB declared receiving honoraria for lectures from Merck, Ferring, and Gedeon Richter. She is a member of ESHRE EXCO, and the Mediterranean Society for reproductive medicine and the president of the Croatian Society for Gynaecological Endocrinology and Reproductive Medicine. CDG is the past Chair of the ESHRE EIM Consortium and a paid deputy member of the Editorial board of Human Reproduction. IR declared receiving reimbursement from ESHRE and EDCD for attending meetings. She holds an unpaid leadership role in OBBCSSR, ECDC Sohonet, and AER. KAR-W declared receiving grants for clinical researchers and funding provision to the institution from the Swedish Cancer Society (200170F), the Senior Clinical Investigator Award, Radiumhemmets Forskningsfonder (Dnr: 201313), Stockholm County Council FoU (FoUI-953912) and Karolinska Institutet (Dnr 2020-01963), NovoNordisk, Merck and Ferring Pharmaceuticals. She received consulting fees from the Swedish Ministry of Health and Welfare. She received honoraria from Roche, Pfizer, and Organon for chairmanship and lectures. She received support from Organon for attending meetings. She participated in advisory boards for Merck, Nordic countries, and Ferring. She declared receiving time-lapse equipment and grants with payment to institution for pre-clinical research from Merck pharmaceuticals and from Ferring. SS-R received research funding from Roche Diagnostics, Organon/MSD, Theramex, and Gedeo-Richter. He received consulting fees from Organon/MSD, Ferring Pharmaceuticals, and Merck Serono. He declared receiving honoraria for lectures from Ferring Pharmaceuticals, Besins, Organon/MSD, Theramex, and Gedeon Richter. He received support for attending Gedeon Richter meetings and participated in the Data Safety Monitoring Board of the T-TRANSPORT trial. He is the Deputy of ESHRE SQART special interest group. He holds stock options in IVI Lisboa and received equipment and other services from Roche Diagnostics and Ferring Pharmaceuticals. KT declared receiving payment for honoraria for giving lectures from Merck Serono and Organon. She is member of the safety advisory board of EDQM. She holds a leadership role in the ICCBBA board of directors. ZV received reimbursement from ESHRE for attending meetings. She also received research grants from ESHRE and Juhani Aaltonen Foundation. She is the coordinator of EHSRE SQART special interest group. The other authors have no conflicts of interest to declare., Disclaimer: This guideline represents the views of ESHRE, which were achieved after careful consideration of the scientific evidence available at the time of preparation. In the absence of scientific evidence on certain aspects, a consensus between the relevant ESHRE stakeholders has been obtained. Adherence to these clinical practice guidelines does not guarantee a successful or specific outcome, nor does it establish a standard of care. Clinical practice guidelines do not replace the need for application of clinical judgement to each individual presentation, nor variations based on locality and facility type. ESHRE makes no warranty, express or implied, regarding the clinical practice guidelines and specifically excludes any warranties of merchantability and fitness for a particular use or purpose (full disclaimer available at https://www.eshre.eu/Guidelines-and-Legal)., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology.)

Background: Ultrasound-guided embryo transfer (US-GET) is a widely performed procedure, but standards for the best practice are not available., Objective and Rationale: This document aims to provide an overview of technical aspects of US-GET after considering the published data and including the preparation for the embryo transfer (ET) procedure, the actual procedure, the post-procedure care, associated pathologies, complications and risks, quality assurance and practitioners' performance., Search Methods: A literature search for evidence on key aspects of the ET procedure was carried out from database inception to November 2021. Selected papers (n = 359) relevant to the topic were analysed by the authors. The following key points were considered in the papers: whether ultrasound (US) practice standards were explained, to what extent the ET technique was described and whether complications or incidents and how to prevent such events were reported. In the end, 89 papers could be used to support the recommendations in this document, which focused on transabdominal US-GET., Outcomes: The relevant papers found in the literature search were included in the current document and described according to the topic in three main sections: requirements and preparations prior to ET, the ET procedure and training and competence for ET. Recommendations are provided on preparations prior to ET, equipment and materials, ET technique, possible risks and complications, training and competence. Specific aspects of the laboratory procedures are covered, in particular the different loading techniques and their potential impact on the final outcomes. Potential future developments and research priorities regarding the ET technique are also outlined., Limitations Reasons for Caution: Many topics were not covered in the literature review and some recommendations were based on expert opinions and are not necessarily evidence based., Wider Implications: ET is the last procedural step in an ART treatment and is a crucial step towards achieving a pregnancy and live birth. The current paper set out to bring together the recent developments considering all aspects of ET, especially emphasizing US quality imaging. There are still many questions needing answers, and these can be subject of future research., Study Funding/competing Interests: No funding. A.D.A. has received royalties from CRC Press and personal honorarium from Cook, Ferring and Cooper Surgical. The other co-authors have no conflicts of interest to declare that are relevant to the content of this article., (© The Author(s) 2022. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology.)

Study Question: To evaluate the implementation of the coding systems in medically assisted reproduction (MAR) centres in the European Union (EU)., Summary Answer: Our data show that a significant number of MAR centres use the Single European Code (SEC), but it also shows certain limitations to the coding., What Is Known Already: Traceability and identification of tissue and cells used for clinical application are extremely important as it is one of the key aspects of quality and safety both for the donors and the recipients. Patients as well as tissues and cells move across the European continent and far beyond, hence a uniform coding system was very much needed. The coding of tissues and cells from human origin was already embedded in the EU directives 2004/23/EC. The use of the Single European Code (SEC) on tissues and cells was enforced in 2017 for tissues and cells distributed within the EU or exported from the EU. The SEC ensures standardization within the EU, allowing the integration of the two existing codes (ISBT-128 and Eurocode) within the SEC structure. Likewise, in the MAR field, the SEC was launched in order to ensure the traceability of reproductive tissues and cells. Gametes and embryos from partner donation as well as reproductive cells and tissues of allogeneic donation were excluded from the SEC as long as they remain in the centre of origin., Study Design Size Duration: A cross-sectional survey aimed to gain insight into the use of SEC by MAR centres was conducted between 5 November and 15 December 2018., Participants/materials Setting Methods: The online survey was distributed among the ESHRE members., Main Results and the Role of Chance: The survey results highlight the strengths and weaknesses in the practical use of the SEC. The data from the survey showed that the SEC code is something that is known in the MAR field. Our data showed that over half of the respondents were using the SEC in their centre. On the other hand, there is also criticism about the use of SEC in MAR, especially that the added value for traceability and identification in ART is found to be rather limited., Limitations Reasons for Caution: The survey response rate was rather low (4.84%). The view of the use of SEC discussed in this paper still provides insight into the use of the SEC in several MAR centres., Wider Implications of the Findings: The survey highlights some knowledge gaps concerning coding. This information can be used to develop tools to increase knowledge of the SEC., Study Funding/competing Interests: There was no external funding for this study. The authors declare that they have no conflict of interest., Trial Registration Number: N/A., (© The Author(s) 2020. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology.)

Study Question: What is good practice in ultrasound (US), and more specifically during the different stages of transvaginal oocyte retrieval, based on evidence in the literature and expert opinion on US practice in ART?, Summary Answer: This document provides good practice recommendations covering technical aspects of US-guided transvaginal oocyte retrieval (oocyte pick up: OPU) formulated by a group of experts after considering the published data, and including the preparatory stage of OPU, the actual procedure and post-procedure care., What Is Known Already: US-guided transvaginal OPU is a widely performed procedure, but standards for best practice are not available., Study Design Size Duration: A working group (WG) collaborated on writing recommendations on the practical aspects of transvaginal OPU. A literature search for evidence of the key aspects of the procedure was carried out. Selected papers ( n  = 190) relevant to the topic were analyzed by the WG., Participants/materials Setting Methods: The WG members considered the following key points in the papers: whether US practice standards were explained; to what extent the OPU technique was described and whether complications or incidents and how to prevent such events were reported. In the end, only 108 papers could be used to support the recommendations in this document, which focused on transvaginal OPU. Laparoscopic OPU, transabdominal OPU and OPU for IVM were outside the scope of the study., Main Results and the Role of Chance: There was a scarcity of studies on the actual procedural OPU technique. The document presents general recommendations for transvaginal OPU, and specific recommendations for its different stages, including prior to, during and after the procedure. Most evidence focussed on comparing different equipment (needles) and on complications and risks, including the risk of infection. For these topics, the recommendations were largely based on the results of the studies. Recommendations are provided on equipment and materials, possible risks and complications, audit and training. One of the major research gaps was training and competence. This paper has also outlined a list of research priorities (including clarification on the value or full blood count, antibiotic prophylaxis and flushing, and the need for training and proficiency)., Limitations Reasons for Caution: The recommendations of this paper were mostly based on clinical expertise, as at present, only a few clinical trials have focused on the oocyte retrieval techniques, and almost all available data are observational. In addition, studies focusing on OPU were heterogeneous with significant difference in techniques used, which made drafting conclusions and recommendations based on these studies even more challenging., Wider Implications of the Findings: These recommendations complement previous guidelines on the management of good laboratory practice in ART. Some useful troubleshooting/checklist recommendations are given for easy implementation in clinical practice. These recommendations aim to contribute to the standardization of a rather common procedure that is still performed with great heterogeneity., Study Funding/competing Interests: The meetings of the WG were funded by ESHRE. The other authors declare that they have no conflict of interest., Trial Registration Number: NA.ESHRE Pages content is not externally peer reviewed. The manuscript has been approved by the Executive Committee of ESHRE., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The evidence-based approach is considered the gold standard of medical guidance. However, for some topics, it may be inappropriate to address them in an evidence-based guideline, as evidence for most of their aspects is absent or limited. Other topics may require only technical recommendations on how to perform a procedure, which are generally not covered in the published literature.In addition to an existing guideline programme, the European Society of Human Reproduction and Embryology has recently developed a manual for the development of (consensus-based) recommendations for good practice. The manual sets out a standardised methodology based on universal guideline principles with the aim of framing and improving the methodological quality of recommendations for good practice documents. The current paper outlines the relevance of recommendations for good practice, the methodology for developing these documents, and the differences and similarities with evidence-based guidelines., Competing Interests: Competing interests: NV and NLC are employed by ESHRE. All authors declare no financial relationships with any organisation that might have an interest in the submitted work in the previous 3 years, no other relationships or activities that could appear to have influenced the submitted work., (© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: The study was aimed to evaluate which factors affect the cumulative live birth rate after elective single embryo transfer in women younger than 36 years. Additionally, number of children in women with more than one delivery per ovum pick-up after fresh elective single embryo transfer and subsequent frozen embryo transfers was assessed., Study Design: Retrospective cohort study analysing data of a university hospital's infertility clinic in 2001-2010. A total of 739 IVF/ICSI cycles with elective single embryo transfer were included. Analyses were made per ovum pick-up including fresh and subsequent frozen embryo transfers. Factors affecting cumulative live birth rates were examined in uni- and multivariate analyses. A secondary endpoint was the number of children born after all treatments., Results: In the fresh cycles, the live birth rate was 29.2% and the cumulative live birth rate was 51.3%, with a twin rate of 3.4%. In the multivariate analysis, having two (odds ratio (OR) 1.73; 95% confidence interval (CI) 1.12-2.67) or ≥3 top embryos (OR 2.66; 95% CI 1.79-3.95) was associated with higher odds for live birth after fresh and frozen embryo cycles. Age, body mass index, duration of infertility, diagnosis or total gonadotropin dose were not associated with the cumulative live birth rate. In cycles with one top embryo, the cumulative live birth rate was 40.2%, whereas it was 64.1% in those with at least three top embryos. Of women who had a live birth in the fresh cycle, 20.4% had more than one child after all frozen embryo transfers. Among women with three or more top embryos after ovum pick-up, 16.1% gave birth to more than one child., Conclusion: The cumulative live birth rate in this age group varies from 40% to 64% and is dependent on the quality of embryos. Women with three or more top embryos have good chance of having more than one child per ovum pick-up without elevated risk of multiple pregnancies., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)