Question: how many days of progesterone before frozen embryo transfer?
Answer: That means maximal endometrial receptivity in a natural 28-day menstrual cycle is from day 19 to day 24. In most IVF clinics worldwide, the practice is to supplement progesterone for 3 days before transferring a cryopreserved day 3 embryo and for 5 days before transferring a cryopreserved day 5 blastocyst.