Extended estrogen administration for women with thin endometrium in frozen-thawed in-vitro fertilization programs

Purpose: To evaluate the effect of extended estrogen administration for women with thin endometrium in frozen-thawed in-vitro fertilization (IVF) programs. Methods: Thirty-six women undergoing IVF program had thin endometrium (<8 mm). Among them, 23 received fresh embryo transfer (control group), but 13 canceled embryo transfer and underwent frozen-thawed embryo transfer in the subsequent cycle after extended administration of exogenous estrogen (study group). Results: In the study group, the mean endometrial thickness increased significantly from 6.7 mm in controlled ovarian hyperstimulation cycles to 8.6 mm after an extended estrogen therapy for 14 to 82 days (P=0.031). Their pregnancy rate was significantly higher than that in the control group (38.5% vs. 4.3%, P=0.016). Among 5 women achieving pregnancies in the study group, one was complicated with placenta accreta, and the other 4 had uneventful pregnancies. Conclusions: Extended estrogen administration followed by frozen-thawed IVF programs is beneficial for women with thin endometrium. However, the risk of abnormal placentation and peripartal complication should be kept in mind.