Objective: To asses the extents to which congenital anomalies affect risk of preterm birth. Methods: For the present study, we analysed data on 1,972,058 newborns registered in the Netherlands Perinatal Registry database (inclusion criteria 16 weeks of gestation). Logistic regression techniques were applied to estimate risks of preterm (< 37 weeks), very preterm (< 32 weeks) and extremely preterm (< 24 weeks) birth for newborns with congenital anomalies. Adjustments were made for neonatal (gender, plurality) and maternal (age, parity, previous abortions, assisted reproductive management, diabetes) characteristics. Results were expressed as odds ratios (ORs). Results: The overall risk of preterm birth was 3.8- fold higher in newborns with congenital anomalies, as compared to newborns without congenital anomalies. Preterm birth risk was elevated in all organ systems, but especially among newborns with congenital anomalies of the central nervous system (OR 8.8) or the respiratory system (OR 5.8), and among newborns with chromosomal or syndromal anomalies (OR 8.0). The overall very preterm and extremely preterm birth risks were respectively 8.4-fold and 11.2-fold higher in newborns with congenital anomalies. Among newborns with anomalies of the central nervous system and among newborns with chromosomal or syndromal anomalies, risks of very preterm birth (ORs 22.1 and 18.6, respectively) and of extremely preterm birth (ORs 37.6 and 31.5, respectively) were much higher. Conclusions: Congenital anomalies are associated with increased risk of preterm birth. Congenital anomalies of the central nervous system and chromosomal or syndromal anomalies are important risk factors for preterm birth.