The measurement of umbilical and uterine artery velocity waveforms was used to study pregnancies complicated by diabetes. Continuous wave Doppler velocimetry was used to identify the umbilical and uterine artery velocity waveforms. A systolic:end diastolic ratio (S:D ratio) was calculated to analyze the obtained velocity waveforms. We treated 33 tightly controlled and monitored diabetic gravidas. The mean blood sugar value for this population was 95 +/- 8 mg/dL, and the mean umbilical artery S:D ratio was 2.5 +/- 0.3. That group of patients was compared to a group on which we reported previously. Statistically significant differences were found between the well-controlled and poorly controlled populations in third-trimester S:D ratios, number of stillbirths and neonatal morbidity. Uterine artery velocimetry allowed the identification of a patient who developed preeclampsia. This study seems to have indicated that umbilical and uterine artery velocimetry may have an adjunctive role in the surveillance of pregnancies complicated by diabetes.