Comparison of the effect of immediate versus delayed transfer following a stimulated IVF cycle on the ongoing pregnancy rate of frozen-thawed embryo transfer cycles: a study protocol for a randomised controlled trial

INTRODUCTION: Frozen-thawed embryo transfer (FET) has become an increasingly important part of in-vitro fertilisation (IVF) treatment. Currently, there is still no good scientific evidence to support when to perform FET following a stimulated IVF cycle. Since all published studies are retrospective and the findings are contradictory, a randomised controlled study is needed to provide Level 1 evidence to guide the clinical practice. METHODS/ANALYSIS: This is a randomised controlled trial. A total of 724 women undergoing the first FET following ovarian stimulation in IVF will be enrolled and randomised according to a computer-generated randomisation list to either (1) the immediate group in which FET will be performed in the first cycle following the stimulated IVF cycle or (2) the delayed group in which FET will be performed at least in the second cycle following the stimulated IVF cycle. The primary outcome is the ongoing pregnancy defined as a viable pregnancy beyond 12 weeks’ gestation. ETHICS AND DISSEMINATION: Ethical approval has been granted by the Ethics Committee of Assisted Reproductive Medicine in Shanghai JiAi Genetics & IVF Institute (JIAI E2017-12) and from the Institutional Review Board of the University of Hong Kong Hospital Authority Hong Kong West Cluster (UW 17–371). A written informed consent will be obtained from each woman before any study procedure is performed, according to good clinical practice. The results of this trial will be disseminated in a peer-reviewed journal. TRIAL REGISTRATION NUMBER: NCT03201783; Pre-results.