Fetal umbilical and internal carotid artery blood flow velocity waveforms during maternal fenoterol administration.

Blood flow velocity waveforms in the fetal umbilical and internal carotid artery were studied during maternal fenoterol treatment in 25 pregnant patients admitted for premature labour between 27 and 35 weeks of gestation. The pulsatility index (PI) from the umbilical artery was significantly reduced (p = 0.02), the PI being situated below the -2 SD limit of the normal reference curve in 28%. There was no statistically significant difference in PI from the umbilical artery when distinguishing between ruptured and unruptured membranes. The reduced pulsatility index of the umbilical artery suggests a decrease in vascular resistance, hence improved utero-placental perfusion. The pulsatility index of the fetal internal carotid artery followed the normal distribution.