Efficacy of Daily 50 Mg Intramuscular Progesterone for Luteal Phase Support in Frozen Embryo Transfer Cycles: Analysis of Serum Levels and Pregnancy Outcomes Publisher



Hatami R ; Shahrokhtehraninejad ES ; Rashidi BH ; Keikha F ; Masoumi M ; Barkhordarioon A ; Tarafdari A
Source: Journal of Family and Reproductive Health Published:2025

Abstract

Objective: To evaluate the efficacy of 50 mg/day intramuscular (IM) progesterone in achieving optimal serum P4 levels during endometrial preparation and investigate the association between serum P4 levels on embryo transfer (ET) day and subsequent fertility outcomes in hormone replacement therapy (HRT) frozen embryo transfer (FET) cycles. Materials and methods: This prospective cohort study included 121 women (aged 22-45 years) undergoing HRT-FET at Imam Khomeini Hospital Complex from December 2022 to January 2024. Endometrial preparation began with oral estradiol valerate (6 mg/day) on cycle day 2. Once an endometrial thickness of ≥8 mm was achieved, daily IM P4 (50 mg) was initiated. Serum P4 levels were measured on ET day, and oral dydrogesterone (20 mg/day) was added for patients with P4 levels <10.0 ng/mL. Primary outcomes included chemical pregnancy, clinical pregnancy, miscarriage, and ongoing pregnancy rates. Results: The mean serum P4 level on ET day was 22.8 ± 10.1 ng/mL, with 78.5% of participants achieving the target range (10-32.5 ng/mL) following IM P4 administration. Overall chemical pregnancy, clinical pregnancy, and ongoing pregnancy rates were 23.1%, 18.2%, and 14.1%, respectively, with a miscarriage rate of 5.0%. Multivariate analysis revealed that P4 levels >27.8 ng/mL were associated with reduced odds of chemical pregnancy (OR = 0.20; 95% CI: 0.05-0.86; p = 0.03), while no significant differences were observed in other pregnancy outcomes across P4 quartiles. Conclusion: Daily administration of 50 mg IM P4 effectively achieved optimal serum P4 levels in most patients. While higher P4 levels (>27.8 ng/mL) were associated with reduced chemical pregnancy rates, the absence of significant correlations with other pregnancy outcomes highlights the multifactorial nature of embryo implantation success. These findings emphasize the need for further research to refine P4 thresholds and identify additional predictive factors influencing pregnancy outcomes in FET cycles. © 2025 Elsevier B.V., All rights reserved.