Evaluation of two luteal support regimens, intramuscular progesterone and progesterone vaginal gel, for vitrified-warmed embryo transfer in women with chronic salpingitis: a single-center 8-year retrospective study

Background Chronic salpingitis is one of the most common causes of female infertility. Luteal support is a critical step for embryo transfer. Here, we evaluated the effects of two luteal support regimens, intramuscular progesterone (IMP) and progesterone vaginal gel (VAG), on the pregnancy outcomes in patients with chronic salpingitis undergoing vitrified-warmed embryo transfer. Methods This study retrospectively analyzed 2240 patients with chronic salpingitis undergoing vitrified-warmed embryo transfer from 2015 to 2022 at our center. Patients were categorized into IMP group (n = 1039) and VAG group (n = 1201). Inverse probability of treatment weighting (IPTW) was used to balance baseline characteristics. Univariate and multivariate logistic regression models were conducted to analyze pregnancy outcomes. Results After IPTW, baseline demographic characteristics were balanced and outcome indicators were comparable. Crude analysis showed a higher live birth rate (OR 1.25, 95% CI 1.017-1.537, p = 0.034) and ongoing pregnancy rate (OR 1.231, 95% CI 1.002-1.512, p = 0.047) as well as lower miscarriage rate (OR 0.612, 95% CI 0.461-0.812, p < 0.001) in IMP group compared with VAG group. After adjusting for confounders, IMP group still presented a higher live birth rate (OR 1.256, 95% CI 1.019-1.547, p = 0.033), ongoing pregnancy rate (OR 1.236, 95% CI 1.004-1.521, p = 0.046) and lower miscarriage rate (OR 0.588, 95% CI 0.443-0.782, p < 0.001). No statistical differences were observed in biochemical pregnancy rate, clinical pregnancy rate, twin pregnancy rate, preterm delivery rate, and full-term delivery rate before and after adjustment. Conclusions For infertile patients with chronic salpingitis undergoing vitrified-warmed embryo transfer, IMP presents greater advantages. VAG may be not recommended as an alternative for luteal support in such patients. These findings, based on our 8-year-long retrospective experience, may contribute to a better selection of luteal support protocol for infertile patients with tubal factors.