[Maternal-fetal circulation in premature labor].

Color and pulsed wave Doppler ultrasonographic studies were performed of the maternal uterine, umbilical, and fetal middle cerebral and renal arteries in 70 singleton preterm pregnancies, within 24 hours of delivery. There were 29 fetuses that had a small weight for gestational age (SGA) at the time of delivery. From these 25 fetuses were small as a result of placental insufficiency. Results of these 25 were compared with a group of 41 fetuses that had appropriate weight for gestational age (AGA). The mean index values of blood flow velocity in the uterine, umbilical, and renal arteries in the 25 intra-uterine growth retarded (IUGR) fetuses were higher (by 9.3-49.3%) than in the AGA preterm fetuses. Indices of middle cerebral artery blood flow were lower (by 18.4-28.5%) in the IUGR fetuses as a result of uteroplacental insufficiency than in AGA fetuses. This reflected a central vasodilatation in the presence of increased peripheral vascular resistance and supported a brain sparing effect of the fetal circulation in the IUGR fetuses. In the other group (of 4 fetuses) the primary mechanism by which these infants were SGA was not uteroplacental insufficiency. The blood flow indices in this small group was similar as in AGA fetuses. This indicates absence of brain-sparing effect in this particular group of affected fetuses. The average weight of 29 SGA fetuses were by 400 gm lower than the weight of 41 AGA preterm fetuses. The average gestational age at the time of delivery of both groups were very similar (31.8 vs. 32.1 weeks).