SUMMARYDiabetes mellitus still represents an important medical problem during pregnancy, causing perinatal morbidity and mortality. Despite improved outcome reflected by a steep decline in perinatal mortality over the past few decades, controversy still exists regarding the care of the pregnant woman with both pre-existing and gestational Diabetes Mellitus. Doppler ultrasound is especially valuable during pregnancy because fetal maternal and placental circulations can be studied.The aim of this work was to study the vascular changes in the uteroplacental and fetoplacental circulations, and to correlate these findings with histopathology of the placenta and placental bed, which may occur in association with diabetic pregnancies.The study was carried out on 100 pregnant women of comparable age and parity. They were divided into 2 groups. The control group comprising 20 normal non-diabetic pregnant women and the normotensive diabetic group comprising 80 pregnant diabetic women. All were singleton pregnancies of 34 weeks or more and were delivered by C.S the control and the study cases were subjected to history taking and thorough physical examination. They were also subjected to ultrasonographic examination for fetal biometric parameters and for Doppler examination. Doppler examination included umbilical artery, uterine arteries fetal middle cerebral artery. At the time of C.S the placenta and placental bed biopsy was obtained. After delivery, the Apgar Score of the newborn was assessed at 1 and 5 minutes, the body weight was measured and the fetus was followed up for any complications.There was a positive correlation between the umbilical artery PI and the mean blood glucose levels indicating that poor diabetic control is probably associated with increased umbilical artery PI. However there was no significant difference between the mean value of the umbilical artery PI in the diabetic and control groups.The uterine arteries Doppler indices showed no significant findings between the diabetic and the control groups. Neither did the uterine arteries Doppler indices show a correlation with the mean blood glucose levels.There was no significant difference between the middle cerebral artery PI in the diabetic and control groups. This observation indicates that there was no redistribution in the fetal circulation in the fetuses of the diabetic group. There was also non correlation between the MCA Doppler indices and the glycemic control.CUR measurements showed no significant difference between the diabetic and the control groups. None of the patients in the control group had an abnormal CUR while in the diabetic group one case showed an abnormally low CUR with a normal middle cerebral artery PI and an abnormally high umbilical PI with reversed diastolic flow. This indicated fetal hypoxia and fetal risk. This fetus had a BPP of 4/8 and died 48 hours after an emergency C.S. CUR is considered an important predictor of fetal morbidity and mortality.Histopathologic studies of the placental bed showed marked difference between the diabetic group and the control group as regards lack of physiologic changes and arteriosclerotic changes, which emphasizes the effect of diabetes on the placental bed vasculature. However, there was no significant correlation between lack of physiologic changes in the placental bed and Doppler indices (umbilical, uterine and CUR), mean blood glucose level or Apgar Score at 5 minutes. Moreover, it was obvious that severe placental bed vascular pathology is associated with smaller birth weight.The placenta of the diabetic group showed much higher incidence of vascular pathologic findings than in the control group. It was also noticed that placentae of diabetic cases had a normal villous structure in 90% of the cases, this might explain the normal uteroplacental, and fetal arterial Doppler indices.