A Randomized Controlled Study of Prolonging the Time of Progesterone Supplementation to Improve the Pregnancy Outcome of Single Day 6 Blastocyst Transfer of Freeze-thaw Cycle

This is a single-center, prospective, randomized controlled study. Patients with single blastocyst transfer in the freeze-thaw cycle, aged from 20 to 38 years, with less than three transfers, and with HRT-cycle single D6 blastocyst transfer in the current cycle were enrolled as the study participants. They were randomized into two groups using an Excel table, and the efficacy was evaluated in a blinded manner by a third party who was unaware of the grouping; the data summary phase was performed by blinded statistical analysis with triple separation of the investigator, operator, and statistician.