Our aim was to assess the long-term outcomes of infants born out of a pregnancy complicated by unexplained polyhydramnios. We retrospectively analysed a cohort of 173 singleton pregnancies with polyhydramnios. There were 24 singletons with unexplained polyhydramnios, defined as polyhydramnios where prenatal testing was negative. Infants were examined by a paediatrician at a median age of 12 months (range 12–64 months). Of the 24 infants, 19 (79%) had a normal outcome. West syndrome, polyuria and pulmonary stenosis were diagnosed in three children during follow up, while there were two perinatal deaths. Paediatric follow up of children born out of pregnancies complicated by unexplained polyhydramnios should be carried out systematically.