Effects of Vaginal vs. Oral Progesterone Supplementation Before Embryo Transfer on Live Birth Rates and Levels: A Randomized Trial.

The increase in frozen embryo transfers is a consequence of advances in embryo vitrification and the implementation of genetic screening of embryos. There is debate over the best progesterone administration route in substituted cycles and the relationship between progesterone levels on embryo transfer day and reproductive outcomes. This trial aimed to compare the clinical results of different progesterone supplementation schedules before embryo transfer and assess the relationship between plasmatic progesterone levels on transfer day and clinical outcomes.