Objectives To determine whether the pre- or postnatal diagnosis of either isolated or non-isolated duodenal obstruction (DO) is associated with different outcomes. Methods A single-center retrospective analysis was carried out of 91 cases diagnosed with a DO between January 1991 and little 2003. Data oil the diagnosis, treatment and outcomes of The cases were gathered, and differences between the groups were analyzed. Results Twenty-eight cases of DO were diagnosed before and 63) after birth. Of 15 presumed isolated cases in the prenatally diagnosed group, four revealed associated or chromosomal anomalies after birth. The types of obstruction present there significantly different between the prenatally (n = 11) and postnatally (n = 27) detected subsets of isolated DO. The prenatally detected subset displayed a lower median gestational age at delivery lower median birth weight and a higher prematurity rate (8/11 vs. 8127). The diagnosis of DO occurred significantly later ill the postnatally defected subset than the postnatal confirmation of the diagnosis in the prenatally detected cases. In the non-isolated cases of DO, no difference was found in the type of chromosomal or associated anomaly or the type of obstruction between the prenatally detected (n = 17) and postnatally detected subsets (n = 36). Trisomy 21 was present in 7/17 (41%) 221,36 (61%) cases, respectively Two terminations and three intrauterine deaths occurred in the prenatal non-isolated subset. The liveborn infants from the prenatally detected non-isolated subset (n = 12) showed a significantly higher prematurity rate (9/12 vs. 14/36), lower median birth weight and earlier conformation of diagnosis after delivery. After surgery, outcome was similar between both subsets of isolated and non-isolated DO. All the infants with all isolated DO survived. Neonatal death occurred in three prenatally and five postnatally diagnosed cases with non-isolated DO. Conclusions The outcome of prenatally and postnatally diagnosed DO is not essentially different despite more prematurity and a lower birth weight lit the former. Of the prenatally detected cases of DO assumed to be isolated, 2,25% revealed additional chromosomal or associated anomalies after delivery, which influenced outcome. Copyright (c) 2008 ISUOG. Published by John Wiley & Sons, Ltd.