Optimal Length of Progesterone Supplementation Before the Transfer of Cryopreserved (Frozen)-Thawed Day 3 Embryos in an Artificial Cycle With Exogenous Estrogen and Progesterone

Cryopreserved-thawed embryos are often replaced in an artificial cycle, in which the endometrium is prepared by exogenous estrogen and progesterone with or without the use of GnRH agonist downregulation. The correct duration for exposure to progesterone is still not well established. To date, there are no prospective randomized trials available, comparing different durations of progesterone supplementation before the date of transfer, with regard to treatment outcome (Nawroth). In this trial, the investigators want to determine the optimal duration of progesterone supplementation: 3 or 5 days before embryo transfer.