Endometriosis as an independent risk factor for preterm birth: a systematic review and meta-analysis of cohort studies

This systematic review and meta-analysis evaluated the association between endometriosis and preterm birth (< 37 weeks). PubMed, Embase, Web of Science, and Cochrane Library were searched through May 2025 for cohort studies. Two investigators independently extracted data and assessed risk of bias using risk of bias in non-randomized studies of interventions (ROBINS-I) and grading of recommendations assessment, development and evaluation (GRADE). Adjusted effect estimates were pooled using a random-effects model. We included 24 studies that involved over 25 million women. Endometriosis was associated with an increased risk of preterm birth (RR = 1.36, 95% CI 1.26–1.46; I² = 85.2%). Subgroup analyses showed increased risk in women who conceived via assisted reproductive technology (ART) (RR = 1.24, 95% CI 1.11–1.38, I 2 = 54.8%) and in women who conceived spontaneously (RR = 1.44, 95% CI 1.28–1.62, I 2 = 36.3%). The association remained consistent across studies with different designs and diagnostic criteria. In the surgically confirmed subgroup (RR = 1.21, 95% CI 1.06–1.39, I² = 0.0%) the association remained significant. Findings remained robust after adjustment for maternal age, parity, and BMI. Current evidence indicates a consistent association between endometriosis and preterm birth, although substantial heterogeneity is observed across the studies. Pregnant women with confirmed endometriosis should receive enhanced prenatal monitoring and risk assessment. This study was registered in PROSPERO (CRD42025100583).