Evidence of fetal cerebral vasodilatation induced by submaximal maternal dynamic exercise in human pregnancy.

To investigate the relationship between maternal exercise and fetal circulatory responses in humans during the third trimester of pregnancy, changes in uterine, umbilical and fetal cerebral circulations were measured by pulsed-Doppler ultrasound method in 14 healthy volunteer pregnant women before and just after a moderate non-exhaustive exercise. Maternal heart rate increased significantly reaching 80% of the theoretical maximal heart rate (TMHR) while uterine resistance indices did not change. The fetal heart rate and umbilical mean velocity were unchanged while umbilical resistance index decreased slightly (0.58 +/- 0.06 versus 0.62 +/- 0.07, P < 0.05). The fetal internal carotid artery mean velocity increased (23.2 +/- 5.3 versus 20.4 +/- 4.1 cm/s, P < 0.02) and the cerebral resistance index decreased (0.71 +/- 0.11 versus 0.80 +/- 0.10, P < 0.01). We conclude that submaximal maternal exercise at 80% of TMHR does not significantly alter uterine perfusion but involves a slight fetal cerebral vasodilation which could be due to a moderate fetal hemoglobin desaturation.