Estrogen Supplementation Mode in HRT-FET Cycle: a RCT

A systematic review and meta-analysis concluded that there is insufficient evidence to recommend one particular protocol for HRT with regard to pregnancy rates after frozen embryo transfer, and no comparison of estrogen dose or route of administration was included in the review\[7\]. It is worth highlighting that the authors did not find any literature discussing the effect of estrogen dose and route of administration for HRT on reproductive outcomes. In 2016, a retrospective cohort study concluded that there is no difference in live birth rates between a constant dose versus an increasing dose of estrogen in oocyte donation cycles with oral or transdermal supplementation\[6\]. In order to provide good evidence about pattern of estrogen supplementation in HRT-FET, a randomized controlled study is urgently needed. The present randomized controlled study aims to compare between a constant estrogen dose protocol and a step-wise increasing estrogen dose protocol on the live birth rate of HRT-FET cycles.