LAUSR

Abstract Objective  Preterm birth (PTB, birth before 37 gestational weeks) is the leading cause of neonatal death and a major challenge for obstetric and neonatal care. About two-thirds of PTBs are spontaneous PTB (sPTB), of which approximately 30% start with preterm premature rupture of membranes (PPROM). The aim of the study was to investigate risk factors and maternal and perinatal outcomes in sPTB with and without PPROM. Study Design  This is a national population-based cohort study including all singleton pregnancies in nulliparous women with spontaneous onset of labor and vaginal births ( n  = 266,968) registered in the Swedish Medical Birth Register 2005 to 2014. sPTB with PPROM (sPTB-PPROM) and sPTB without PPROM were compared regarding risk factors and maternal and perinatal outcomes. Logistic regression was used to estimate adjusted odds ratios (aORs) with 95% confidence intervals (CIs). Adjustments were made for maternal age, body mass index, country of birth, smoking, chronic hypertension, pregestational and gestational diabetes, and gestational length. Results  sPTB-PPROM ( n  = 5,037), compared with sPTB without PPROM ( n  = 8,426), was more common in women with previous spontaneous abortions, prepregnancy urinary tract infections, chronic hypertension, and gestational diabetes and had a higher risk of postpartum endometritis (aOR: 2.78, 95% CI: 1.55–5.00). Infants born to women with sPTB-PPROM had a lower risk of birth asphyxia (aOR: 0.60, 95% CI: 0.43–0.83), respiratory distress syndrome (aOR: 0.86, 95% CI: 0.70–1.00), retinopathy of prematurity (aOR: 0.93, 95% CI: 0.92–0.94), necrotizing enterocolitis (aOR: 0.95, 95% CI: 0.94–0.96), and higher risk of hypoglycemia (aOR: 1.14, 95% CI: 1.01–1.28), and hyperbilirubinemia (aOR: 1.28, 95% CI: 1.19–1.38) compared with infants born to sPTB without PPROM. Conclusion  Our findings of risk factors and distinct differences in adverse outcomes after sPTB-PPROM compared with sPTB without PPROM are of vital importance and might serve as a basis when elaborating programs for the prevention and management of PPROM. Key Points This is a large cohort study of spontaneous preterm birth (sPTB). Singleton nulliparous sPTB with/without preterm premature rupture of membrane (PPROM) were studied. Distinct differences in adverse perinatal outcomes in sPTB with and without PPROM were observed.