How to Rescue Hormonal Replacement Frozen Embryo Transfer Cycle With Low Serum Progesterone? A Randomized Control Trial.

Frozen embryo transfer (FET) is increasingly adopted strategy in modern IVF. Among the many factors that have contributed to such change, the pursuit of an ovarian hyperstimulation syndrome free clinic has been strongly required. Improvements in the vitrification and warming processes and the excellent cryo-survival rates have turned FET in our main tool for preventing this complication. Moreover, a freeze all strategy has proven to provide excellent or even better pregnancy rates (PRs), not only in high but also in normal responders.

While ART have rapidly evolved in the areas of embryo culture, vitrification and understanding of the embryo development, little progress has been achieved regarding endometrial preparation for FET. Undoubtedly, correct implantation requires a good quality embryo and a suitable decidualized endometrium. Artificial cycles require hormone replacement treatment (HRT) with estradiol and progesterone (P4). However, there is not a single standardized treatment described for optimal endometrial preparation and no protocol has proven superiority in terms of reproductive outcomes.(5, 6) Although artificial preparation is the most convenient method to schedule FET cycles, recent reports have highlighted a potentially detrimental effect of low P4 levels prior to FET on miscarriage and live birth rates (LBRs). These results have been observed both in homologous and oocyte recipient FET cycles(7, 8), but also in FET cycles of embryos that had undergone PGT for aneuploidies (PGT-A).(9) Additional P4 supplementation may be a way to improve reproductive outcomes in these patients.

Our open labelled randomized control study aims to investigate whether patients with low serum P4 levels the day before FET under standard HRT can benefit in terms of clinical and ongoing pregnancy and implantation rates from an individualized luteal phase support consisting in the addition of oral dydrogesterone supplementation or daily subcutaneous P4 injection.