Oral versus transdermal oestrogen delivery for endometrial preparation before embryo transfer: a prospective, comparative, randomized clinical trial.

Research Question: To determine whether the transdermal route is equal or superior to the oral route, when preparing the endometrium with oestrogens for embryo transfer.

Design: Prospective, randomized controlled trial; 140 patients randomized; the pills group followed a protocol with oestradiol valerate pills and the patches group followed a protocol with oestradiol hemihydrate patches. The primary variable was endometrial thickness on day 10 ± 1 of treatment.