ESHRE guideline: number of embryos to transfer during IVF/ICSI†.

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.

Evidence and consensus on technical aspects of embryo transfer.

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.

Top-quality embryo transfer is associated with lower odds of ectopic pregnancy.

Introduction: The incidence of ectopic pregnancy is up to four times higher after in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) than in spontaneous pregnancies, and the risk of ectopic pregnancy is increased by tubal factor infertility and the transfer of multiple embryos. However, the effect of embryo quality on the probability of ectopic pregnancy has not been investigated until now and it is not clear whether ovarian stimulation parameters affect the incidence of ectopic pregnancy.

Material And Methods: An historical cohort study of 15 006 clinical pregnancies (diagnosed by ultrasound at 6-8 gestational weeks) after non-donor IVF/ICSI with fresh embryo transfer (n = 8952) or frozen-thawed embryo transfer (n = 6054).

Evaluating risk, safety and efficacy of novel reproductive techniques and therapies through the EuroGTP II risk assessment tool.

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.

Coding in medically assisted reproduction: the status of the implementation of the Single European Code for reproductive cells and tissues.

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.

Recommendations for good practice in ultrasound: oocyte pick up.

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.

European Recommendations for good practice in addition to an evidence-based guidelines programme: rationale and method of development.

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.

Embryo quality is the main factor affecting cumulative live birth rate after elective single embryo transfer in fresh stimulation cycles.

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.

Factors affecting the outcome of frozen-thawed embryo transfer.

Study Question: Which clinical and laboratory factors affect live birth rate (LBR) after frozen-thawed embryo transfer (FET)?

Summary Answer: Top quality embryo characteristics, endometrial preparation protocol, number of embryos transferred and BMI affected independently the LBR in FET.

What Is Known Already: FET is an important part of present-day IVF/ICSI treatment. There is limited understanding of the factors affecting success rates after FET.

Elective single embryo transfer with cryopreservation improves the outcome and diminishes the costs of IVF/ICSI.

Background: Although elective single embryo transfer (eSET) minimizes the multiple birth rate after in vitro fertilization (IVF)/intra cytoplasmic sperm injection (ICSI), there remain concerns in many countries that it is less effective and more expensive than conventional double embryo transfer (DET).

Methods: We compared the clinical outcome achieved in the years 1995-1999, in which eSET was rarely used (4.2% of women, DET period) with that of the years 2000-2004, in which eSET was more widely used (46.

High and low BMI increase the risk of miscarriage after IVF/ICSI and FET.

Background: The extremes of BMI are associated with an increased risk of miscarriage both in spontaneously conceived pregnancies and after fertility treatment. The aim of the present study was to study the effect of BMI on miscarriage rate (MR) in fresh IVF/ICSI, and in spontaneous and hormonally substituted frozen-thawed embryo (FET) cycles.

Methods: Analysis was carried out on 3330 first pregnancy cycles, performed during the years 1999-2004, of which 2198 were fresh, 666 were spontaneous and 466 were hormonally substituted FET cycles.

Elective single embryo transfer in women aged 36-39 years.

Background: The elective single embryo transfer policy is the only effective strategy known to minimize the risk of multiple pregnancy. However, little is known about its applicability to women older than 35 years.

Methods: Analysis was carried out on 1224 fresh IVF/ICSI cycles with embryo transfer and 828 frozen embryo transfer (FET) cycles of women aged 36-39 years.

An initial low response predicts poor outcome in in vitro fertilization/intracytoplasmic sperm injection despite improved ovarian response in consecutive cycles.

Objective: To study the predictive value of initial low response (LR) in IVF/intracytoplasmic sperm injection (ICSI).

Design: Retrospective analysis.

Setting: Two Finnish fertility centers.