Perinatal outcomes in pregnancies with and without polycystic ovary syndrome assessed by the Composite Adverse Perinatal Outcome score: a propensity score–matched retrospective study

Aims: To quantify severity-weighted perinatal morbidity in pregnancies complicated by polycystic ovary syndrome (PCOS) using the Composite Adverse Perinatal Outcome (CAPO) score and to assess robustness after propensity score matching and BMI-focused sensitivity analyses.Methods: We conducted a two-center retrospective cohort study (January 2022-October 2025). Among 3.616 eligible singleton deliveries, 318 (8.8%) had documented PCOS. Propensity scores were estimated using maternal age, gravidity, parity, prior abortion/miscarriage, and prior curettage. Using 1:1 nearest neighbor matching (caliper 0.2 SD logit), 262 PCOS pregnancies were matched to 262 controls. CAPO total and subscores were compared in matched pairs; BMI-adjusted conditional regression was performed. Sensitivity analyses included BMI-stratified comparisons and BMI-inclusive rematching.Results: In the matched cohort (n=524), CAPO total scores were higher in PCOS pregnancies (median [IQR] 150 [0-280] vs 75 [0–200]; p=0.004), and CAPO>0 occurred more frequently (45.0% vs 36.3%; p=0.02). PCOS remained associated with higher CAPO after BMI adjustment (β=+40.2; 95% CI 14.3-66.1; p=0.003). PCOS pregnancies had higher rates of severe preeclampsia, postpartum hemorrhage, preterm birth, low birth weight, and neonatal intensive care unit (NICU) admission >24 h. Under BMI-inclusive matching, 244 pairs were retained with balanced BMI (SMD=0.04); CAPO differences were attenuated but persisted (p=0.045; β=+22.5, p=0.024). Conclusion: PCOS pregnancies show a higher severity-weighted perinatal morbidity burden by CAPO, distributed across hypertensive and prematurity-linked outcomes. Associations persisted after BMI adjustment and conservative BMI-inclusive sensitivity analyses, suggesting that adiposity explains part but not all-of the excess morbidity signal.