Fetal internal carotid artery pulsed Doppler flow velocity waveforms and maternal plasma glucose levels.

Eighteen women at 32-36 weeks' gestation were studied by pulsed Doppler (duplex) for recording blood flow velocity waveforms from the umbilical artery and fetal intracranial internal carotid artery. The pulsatility index was calculated for each artery separately. Each subject was investigated when fasting and 1 hour after a 100-g glucose load. Increases in maternal plasma glucose concentration of 30 mg/dL or more were followed by elevation of the mean pulsatility index in the umbilical artery from 0.9 +/- 0.22 to 1.08 +/- 0.18 (P less than .01) and in the internal carotid artery from 1.17 +/- 0.19 to 1.8 +/- 0.47 (P less than .001). The findings suggest a compensatory increase in cerebrovascular resistance during increases in glucose levels.