Modified natural and optimized programmed frozen embryo transfers have equivalent live birth rates: an analysis of 6,682 cycles

Document Type


Publication Date



Obstetrics & Gynecology

Journal Title

Fertility and Sterility


OBJECTIVE: To compare live birth rates in modified natural and programmed single blastocyst frozen embryo transfer (FET) cycles. DESIGN: Retrospective cohort study. SETTING: University affiliated fertility practice. PATIENT(S): Patients undergoing single blastocyst FETs between January 2014 and December 2019. A total of 15,034 FET cycles from 9,092 patients were reviewed; 1,186 modified natural and 5,496 programmed FET cycles from 4,532 patients met inclusion criteria for analysis. INTERVENTION(S): No intervention. MAIN OUTCOME MEASURE(S): The primary outcome measure was live birth rate. RESULTS: There was no difference in live birth after programmed cycles using intramuscular (IM) progesterone or combination vaginal and IM progesterone compared to modified natural cycles [aRR 0.94 (0.85-1.04)] and [0.91 (0.82-1.02)], respectively. Relative risk of live birth was decreased, compared to modified natural cycles, in programmed cycles that used exclusively vaginal progesterone [aRR 0.77 (0.69-0.86)] CONCLUSION(S): Live birth rate was decreased in programmed cycles that used only vaginal progesterone. However, no difference in live birth rates existed between modified natural and programmed cycles if programmed cycles used either IM or combination IM and vaginal progesterone protocols. This study demonstrates that modified natural FET cycles and optimized programmed FET cycles have equivalent live birth rates.