Objectives: It was the aim of this study to determine if prenatal diagnosis of congenital duodenal obstruction (CDO) selects high-risk pregnancies and demands special perinatal attention. Methods: Medical records of 62 neonates with intrinsic CDO, admitted since 1981 in 2 institutions, were reviewed and divided into 2 groups: 39 cases, detected in utero by a prenatal ultrasonogram (group A), and 23 diagnosed at birth (group B). Prevalence of complete CDO, mean gestational age, mean birth weight, hydramnios, as well as maternal-foetal complications requiring emergency Caesarean section and associated with premature delivery were compared in the 2 groups. Results: A complete CDO was found in 77% of patients in group A versus 48% of patients in group B (p < 0.02). Differences in mean gestational age and mean birth weight in the 2 groups were non-significant. Prenatally diagnosed patients presented a higher prevalence of hydramnios, maternal-foetal complications and premature delivery. Conclusions: Prenatal diagnosis selects patients with complete CDO and hydramnios. These pregnancies present a high incidence of maternal-foetal complications, which may require an emergency Caesarean section, and are frequently associated with premature delivery. These aspects must be considered in prenatal counselling. In utero transfer to a tertiary centre for delivery and appropriate perinatal care should be recommended.