Systolic/diastolic ratios of umbilical velocimetry have been used to assess downstream placental vascular resistance. Reverse end-diastolic flow velocity during end diastole suggests extreme abnormality in waveform and resistance. We reviewed our experience of patients showing reverse end-diastolic flow velocity over a 2 1/2-year period. Out of 550 high-risk patients studied with umbilical velocimetry over this period, 12 patients showed the finding. All patients were delivered of small for gestational age fetuses and the perinatal mortality in this group was 50%. There was also significant perinatal morbidity as judged by cesarean section performed because of fetal distress, low Apgar scores, days in neonatal intensive care, prematurity, placental infarcts, and lethal anomalies. These findings suggest that reverse end-diastolic velocity on umbilical velocimetry is associated with catastrophic perinatal outcome, and aggressive perinatal management may be advised in this group of patients.