Antepartum ultrasound scans of seven pregnancies complicated by fetal triploidy were reviewed. Estimated gestational age (EGA) by ultrasound lagged EGA by last menstrual period in six of seven patients. Normal interval growth of biparietal diameter in the second trimester was demonstrated in all fetuses that had serial scans. Sonographic features commonly associated with fetal triploidy; such as oligohydramnios and cephalocorporal disproportion, were seen in only two cases. Fetal anomalies were evident by ultrasound in five of seven patients. Six of seven patients had partial moles. All of these patients had placentas that appeared abnormal. The ultrasound appearance of the placenta, however, was not the same with each case. Therefore, sonographic features of pregnancies complicated by fetal triploidy are not uniform and the diagnosis cannot be made by ultrasound alone.