This study reports the maternal, fetal, and neonatal outcomes in cases with hypoplastic umbilical artery. The sonographic finding of a three-vessel umbilical cord showing an artery-to-artery diameter difference of more than 50 per cent was defined as hypoplastic umbilical artery. All fetuses diagnosed with hypoplastic umbilical artery underwent genetic amniocentesis and ultrasound. Fetal, maternal, and neonatal outcomes were analysed. Twelve fetuses with hypoplastic umbilical artery were detected over a 6-year period (1989-1995). Associated abnormalities included trisomy 18 (one case), polyhydramnios (three cases), congenital heart disease (one case), and fetal growth restriction (two cases). Maternal diabetes was detected in four cases. The pregnancy was terminated in one case; one neonate with severe fetal growth restriction expired; and one survived with congenital heart disease. The presence of hypoplastic umbilical artery was associated with increased perinatal morbidity and congenital abnormalities. Diabetes was frequently detected. Fetal surveillance and echocardiography are indicated in cases of hypoplastic umbilical artery.