- Objective: To determine whether congenital anomalies are associated with a high rate of neonatal morbidity in preterm birth. Study design: 312 singletons (22–36 wk) with congenital anomalies that were delivered preterm were compared with a random sample of 936 preterm singleton without congenital anomalies. Data was obtained using the computerized birth discharge records. Statistical analysis included univariate and multivariate logistic regression analyses. Results: Three thousand five hundred and seventy-eight (3578) women with preterm births met the inclusion criteria (singleton with prenatal care). The prevalence of congenital anomalies in the study population was 8.7% (312/3578). Gestational age at delivery was significantly lower in the congenital anomaly group compared with the control (32.0±3.7 SD vs. 34.4±2.7 SD; p<0.001). The following pregnancy complications were higher in the group with congenital anomalies than in those without anomalies: severe pregnancy induced hypertension (PIH), hydramnions, oligohydramnion, intrauterine growth restriction (IUGR), fetal distress, cesarean section, malpresentation and mal position, abruption placenta, meconium stained amniotic fluid, 1 min Apgar score (<2), 5 min Apgar score (<7). Perinatal mortality rates in 28–32 wk and 33–36 wk were significantly higher in the group with congenital anomalies than in the control group. Neonatal morbidity data (necrotizing enterocolitis, respiratory distress syndrome, bronchopulmonary dysplasia, intraventricular hemorrhage, and sepsis) was available for 909 neonates (239 with congenital anomalies and 670 without congenital anomalies). After adjusting for gestational age, the presence of congenital anomalies remained strongly associated with neonatal morbidity (having one or more of the above mentioned conditions) (adjusted OR: 5.3, 95% CI 3.4–9.2). When adjusting for other confounding variables, congenital anomalies were strongly associated with neonatal morbidity (OR: 6.44, 95% CI 3.94–10.51), and perinatal mortality (OR: 3.08, 95% CI 2.04–4.65). In terms of attributable fraction in our population of preterm births, the proportion of neonatal morbidity and the proportion of perinatal mortality attributable to congenital malformation is 32% and 15%, respectively. Conclusion: Congenital anomalies in preterm birth are associated with a higher rate of pregnancy complications and are an independent risk factor for neonatal morbidity and perinatal mortality.