OBJECTIVE To investigate prenatal ultrasonographic findings associated with megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS). METHODS A PubMed search was performed using the terms 'MMIHS', 'MMIH' and 'prenatal diagnosis'. RESULTS A total of 50 cases were analyzed. Prenatal diagnosis was achieved in 26% of cases. In 54% of patients with a correct antenatal diagnosis there was a previously affected sibling. Fetal megacystis with or without hydroureteronephrosis was the most common initial ultrasonographic finding (88%). While megacystis eventually complicated all fetal presentations, isolated bilateral hydronephrosis and isolated dilated stomach were noted (in 10 and 2% of cases, respectively) prior to megacystis. The initial sonographic abnormality was most commonly detected (in 70% of patients) in the second trimester. Amniotic fluid was normal in 69% and increased in 27% of cases. Gastrointestinal abnormalities were noted in 24% of pregnancies. CONCLUSIONS MMIHS should be prenatally suspected when fetal megacystis is associated with a normal or increased amount of amniotic fluid and normal external genitalia, especially in the setting of a suggestive family history. Associated gastrointestinal findings support this diagnosis. Isolated bilateral hydronephrosis may precede the development of megacystis. Due to preserved renal function and a general absence of oligohydramnios, no rationale exists for vesicoamniotic shunt placement.