Labarta E, et al. - Researchers in this work determined whether there is a relationship between serum progesterone (P) and endometrial volume on the day of embryo transfer (ET) with ongoing pregnancy rate (OPR) in artificial endometrium preparation cycles. Findings revealed that patients with serum P < 9.2 ng/ml on the day of ET had a significantly lower OPR. However, no association was observed between endometrial volume and OPR.