Intramuscular route of progesterone administration increases pregnancy rates during non-downregulated frozen embryo transfer cycles.

ObjectiveThe optimal route of progesterone (P4) administration in embryo transfer (FET) cycles remains to be determined. The objective of this study is to compare the pregnancy outcomes between intramuscular (IM) and vaginal progesterone (PV) administration for endometrial preparation in non-donor FET cycles.Study designA retrospective clinical study in a private practice infertility setting.ResultsNo significant differences in patient demographics and embryo characteristics were noted between the two groups. The clinical pregnancy rate as well as the live birth rate were significantly higher in the IM arm compared to the PV arm (38.2% vs 28%, 34.5 % vs 22.8%, respectively).ConclusionAlthough both routes of progesterone administration had similar rates of initial positive pregnancy tests, the IM route had a significantly higher live birth rate. The exact reason for this difference remains to be determined.