The prevalence of late-follicular phase progesterone elevation and impact on the ongoing pregnancy rate after fresh and frozen blastocyst transfer. Sub-study of an RCT.

The effect of late-follicular phase progesterone elevation (LFPE) during ovarian stimulation on reproductive outcomes in ART treatment remains controversial, but recent studies indicate lower pregnancy rates with rising progesterone levels. This study aims to investigate the prevalence of late-follicular phase progesterone elevation (LFPE) and possible impact on ongoing pregnancy rate after fresh or frozen blastocyst transfer in a sub-study setting of a randomised controlled trial. A total of 288 women were included (n=137 and n=151 in the fresh transfer and freeze-all group, respectively). Among these 11(3.8%) had a progesterone level ≥1.5 ng/ml, and 20(6.9%) had a progesterone level ≥1.2 ng/ml on