In a case of complete trisomy 9, ultrasound findings led to prenatal diagnosis. This case is reviewed in the context of previous case reports. A 29-year-old gravida III, para II was referred at 34 weeks because of abnormal ultrasound findings. The findings included intrauterine growth retardation, Dandy-Walker malformation, a single atrium, liver calcifications, a two-vessel cord, and abnormal Doppler studies. Percutaneous umbilical blood sampling revealed complete trisomy 9. Prenatal diagnosis led to a plan of no intervention for fetal indications. Autopsy revealed facial, cardiovascular, central nervous, and skeletal findings frequently seen in complete trisomy 9. Review of all cases showed that 12 of 15 (80%) occurred in mothers younger than 35 years, 11 of 13 cases (85%) delivering after 23 weeks' gestation were small for gestational age, and 7 of 12 liveborns (58%) had cesarean delivery. Only 3 of 12 liveborns (25%) lived beyond 7 days. Abnormal ultrasound findings can be seen in cases of complete trisomy 9. Prenatal diagnosis allows the parents to make an informed decision regarding fetal intervention, which may avoid unnecessary cesarean delivery.