Combined real‐time Doppler ultrasound blood flow measurements were carried out in 20 diabetic pregnant women in the third trimester. The placenta morphology was examined with emphasis on maturation, centrocotyledon hemorrhage, villous edema, and ischemia, ischemic villitis, infarction, perivillous fibrin deposition, thrombosis, and inflammatory changes of membranes and fetal placental vessels. Ten out of 17 cases with placenta pathology had normal blood flow measurements. Centrocotyledon hemorrhage (n = 8) was associated with a higher pulsatility index in the fetal aorta and development of fetal distress and obstetric intervention in labor. The higher number of hemorrhages, the greater the risk of intervention. The pulsatility index was normal in the umbilical artery. The uterine artery pulsatility index showed no correlation to the hemorrhages. Ischemic villitis and infarction were not found in any placenta, suggesting that there were no cases of advanced placental dysfunction. Placental immaturity, found in 11 cases, was not associated with any flow anomalies. Centrocotyledon hemorrhage seemed to be the earliest morphological abnormality affecting blood flow in the feto‐maternal circulation in diabetic pregnancy. Centrocotyledon hemorrhage might be the first sign of placental microflow disturbance, possibly affecting fetal oxygenation, but not the total placental vascular bed resistance.