Comparison of pregnancy outcome after adding oral or intramuscular progesterone to vaginal progesterone in frozen embryo transfer: A cross-sectional study.

Background: Currently, frozen embryo transfers (FET) account for 41% of all embryo transfer cycles. Vaginal progesterone preparations have become the leading choice for luteal phase support due to their convenient application; however, using only vaginal progesterone during FET cycles results in a lower ongoing pregnancy rate. Objective: This study aimed to investigate whether replacing intramuscular (IM) progesterone with oral dydrogesterone in FET cycles affects pregnancy outcomes or not. Materials and Methods: In this cross-sectional study, pregnancy outcomes were analyzed in women who underwent cleavage stage FET during an endometrial preparation cycle using hormone replacement therapy at Yazd Reproductive Sciences Institute, Yazd, Iran, between April 2023 and November 2023. The study examined 2 groups based on a luteal phase support regimen: the dydrogesterone group, which received vaginal progesterone and oral dydrogesterone, and the IM progesterone group, which received vaginal progesterone and IM progesterone. Data were extracted from patient files to compare outcomes between the 2 groups. Results: A total of 960 cycles meeting the inclusion criteria were analyzed, with 292 women in the dydrogesterone group and 668 women in the IM progesterone group, and pregnancy outcomes were compared between the 2 groups. The chemical pregnancy rates (28.4% vs. 29.9%, p = 0.636), clinical pregnancy rates (25.3% vs. 26.9%, p = 0.604), and ongoing pregnancy rates (21.9% vs. 23.8%, p = 0.525) were lower and miscarriage rates (14.7% vs. 11.7%, p = 0.210) were higher in dydrogesterone group compared to IM progesterone group, although this difference was not statistically significant. Conclusion: Based on the ease of use and similar pregnancy outcomes of oral dydrogesterone, it can potentially replace the daily injections of IM progesterone.