Live Birth Rate of Fresh Embryo Transfer with GnRH Agonist Long Protocol is Higher Than Frozen Embryo Transfer

Abstract

Background: Along with progress in embryo cryopreservation, especially in vitrification has made freeze all strategy more acceptable. Some studies found comparable or higher live birth rate with frozen embryo transfer (FET) than with fresh embryo transfer（ET）in gonadotropin releasing hormone antagonist (GnRH-ant) protocol. But there were no reports about live birth rate differences between fresh ET and FET with gonadotropin releasing hormone agonist (GnRH-a) long protocol. The aim of this study is to analyze whether patients benefit from freeze all strategy in GnRH-a protocol from real-world data.Methods: This is a retrospective cohort study, in which women undergoing fresh ET or FET with GnRH-a long protocol at Chongqing Reproductive and Genetics Institute from January 2016 to December 2018 were evaluated. The primary outcome was live birth rate. The secondary outcomes were implantation rate, clinical pregnancy rate, pregnancy loss and ectopic pregnancy rate.Results: A total of 7,814 patients met inclusion criteria, implementing 5,216 fresh ET cycles and 2,598 FET cycles, respectively. The demographic characteristics of the patients were significantly different between two groups, except BMI. After controlling for a broad range of potential confounders (including age, infertility duration, BMI, AMH, no. of oocytes retrieved and no. of available embryos), multivariate logistic regression analysis demonstrated that there was no significant difference in terms of clinical pregnancy rate, ectopic pregnancy rate and pregnancy loss rate between two groups (all P>0.05). However, the implantation rate and live birth rate of fresh ET group were significantly higher than FET group (P<0.001 and P=0.012, respectively).Conclusion: Compared to FET, fresh ET following GnRH-a long protocol could lead to higher implantation rate and live birth rate in infertile patients underwent in vitro fertilization (IVF). The freeze all strategy should be individualized and made with caution especially with GnRH-a long protocol.