Immediate versus postponed single blastocyst transfer in modified natural cycle frozen embryo transfer (mNC-FET): a study protocol for a multicentre randomised controlled trial

Abstract

Introduction Today, it is widespread practice to postpone frozen embryo transfer (FET) in a modified natural cycle (mNC) for at least one menstrual cycle after oocyte retrieval and failed fresh embryo transfer or freeze-all. The rationale behind this practice is the concern that suboptimal ovarian, endometrial or endocrinological conditions following ovarian stimulation may have a negative impact on endometrial receptivity and implantation. However, two recent systematic reviews and meta-analyses based on retrospective data did not support this practice. As unnecessary delay in time to transfer and pregnancy should be avoided, the aim of this study is to investigate if immediate single blastocyst transfer in mNC-FET is non-inferior to standard postponed single blastocyst transfer in mNC-FET in terms of live birth rate. Methods and analysis Multicentre randomised controlled non-blinded trial including 464 normo-ovulatory women aged 18–40 years undergoing single blastocyst mNC-FET after a failed fresh or freeze-all cycle. Participants are randomised 1:1 to either FET in the first menstrual cycle following the stimulated cycle (immediate FET) or FET in the second or subsequent cycle following the stimulated cycle (postponed FET). The study is designed as a non-inferiority trial and primary analyses will be performed as intention to treat and per protocol. Ethics and dissemination Ethical approval has been granted by the Scientific Ethical Committee of the Capital Region of Denmark (J-nr.: H-19086300). Data will be handled according to Danish law on personal data protection in accordance with the general data protection regulation. Participants will complete written consent forms regarding participation in the study and storage of blood samples in a biobank for future research. The study will be monitored by a Good Clinical Practice (GCP)-trained study nurse not otherwise involved in the study. The results of this study will be disseminated by publication in international peer-reviewed scientific journals. Trial registration number NCT04748874; Pre-results.

Individual-level air pollutants exposure and pregnancy outcomes in patients who underwent assisted reproductive technology: A retrospective longitudinal cohort study

“…Presently, if it occurs a failed fresh transfer or freeze-all cycle, according to the acknowledged standard clinical practice, FET cycles treatment will be performed again after one menstrual cycle at least. 32 Besides, compare to spontaneous conception and FET, patients receiving fresh transfer cycles are more easily to be experienced damaged endometrial receptivity and embryo implantation, and high odds of preterm birth and lower birthweight. 33 Therefore, we performed this individual-level retrospective longitudinal cohort study in Hefei, Anhui Province, China to comprehensively investigate the effects of monthly exposure to six criteria air pollutants on pregnancy outcomes among women undergoing IVF or ICSI cycle and meanwhile explore the possible effect modifiers.…”