Intramuscular progesterone versus 8% Crinone vaginal gel for luteal phase support following blastocyst cryopreserved single embryo transfer: a retrospective cohort study.

BACKGROUND: The optimal route of progesterone administration for luteal support in cryopreserved embryo transfer (CET) has been the subject of much debate. While most published research has pertained to day 3 transfers, recent data on blastocyst CET has suggested that intramuscular progesterone (IMP) is superior to twice daily vaginal Endometrin suppositories for luteal phase support, resulting in significantly higher ongoing pregnancy rates. This study aimed to determine whether IMP is similarly superior to 8% Crinone vaginal gel for luteal phase support following blastocyst CET. METHODS: Autologous and donor oocyte blastocyst cryopreserved single embryo transfer (SET) cycles from January 2014-January 2019 utilizing either 50 mg IMP daily or 90 mg 8% Crinone gel twice daily for luteal support were included. The primary outcome was live birth. Secondary outcomes included biochemical pregnancy, spontaneous abortion, and clinical pregnancy. All analyses were adjusted a priori for oocyte age. Log-binomial regression analysis was performed with differences in outcomes reported as relative risk (RR) with 95% confidence intervals (CI). RESULTS: A total of 1710 cycles were included, of which 1594 utilized IMP and 116 utilized 8% Crinone gel. Demographic and cycles characteristics were similar between the two groups. Compared to cycles utilizing IMP, cycles utilizing Crinone gel resulted in similar rates of live birth (RR 0.91; 95% CI 0.73-1.13), biochemical pregnancy (RR 1.12, 95% CI 0.65-1.92), spontaneous abortion (RR 1.41, 95% CI 0.90-2.20), and clinical pregnancy (RR 1.00, 95% CI 0.86-1.17). CONCLUSIONS: Compared to cryopreserved blastocyst SET cycles utilizing IMP for luteal support, cycles utilizing 8% Crinone gel resulted in similar likelihood of live birth.