Doppler assessment of fetal blood flow velocity waveforms during acute maternal oxygen administration as predictor of fetal outcome in post-term pregnancy.

The changes in fetal blood flow velocity waveforms during maternal administration of 60% humidified oxygen were assessed by Doppler ultrasonography in 45 post-term fetuses. During oxygen treatment, nine fetuses exhibited temporary increases (24.3 +/- 2.0% [1 standard deviation] above pretreatment values) in the pulsatility index at the level of internal carotid artery. Although no significant changes (2.9 +/- 5.1%) were found in the remaining 36 fetuses. In this former group a higher incidence of emergency cesarean delivery due to fetal distress and more neonatal complications were observed. Also, meconium staining of the amniotic fluid and low 1- and 5-minute Apgar scores occurred more frequently in the group of fetuses who responded to maternal oxygen administration. An increase of at least 20% in the pulsatility index of internal carotid artery during maternal hyperoxygenation may be a useful marker of adverse outcome in post-term fetuses.