Additional Daily Intramuscular Progesterone For Luteal Phase Support Does Not Improve Live Birth Rates of Programmed Frozen-Thawed Embryo Transfer Cycles

Abstract

This retrospective cohort study aims to investigate whether additional daily intramuscular progesterone (IMP) for luteal phase support improves live birth rates of programmed frozen-thawed embryo transfer (FET) cycles. The study was conducted at a tertiary university hospital assisted reproductive technology (ART) center between January 2014 and Jan 2021. Six hundred four infertile patients with single-day 5-6 frozen-thawed blastocyst embryo transfer were enrolled in the study. All patients received either 8% micronized vaginal gel or vaginal progesterone capsules for luteal phase support. Intramuscular progesterone was added to vaginal progesterone depending on the in vitro fertilization (IVF) specialist’s choice. Luteal phase support (LPS) was started 6 days before transfer in frozen-thawed cycles and continued until the end of the first trimester. Cycles were compared depending on vaginal progesterone types (8% gel vs. capsule) and the presence of intramuscular progesterone. The primary outcome was the live birth rate. A total of 604 FET cycles were enrolled. Using 8% micronized progesterone or progesterone capsules did not change the live birth rates (24% vs. 25.9%). As the main result, intramuscular progesterone support with vaginal progesterone compared with only vaginal progesterone did not improve the live birth results (22% vs. 24%). In conclusion, this study demonstrated that routine IMP progesterone given in combination with vaginal progesterone does not improve ART outcomes. This combination may be beneficial in a selective population with a monitored luteal phase. Using any form of vaginal progesterone alone is adequate for LPS.