Fetal oxygen saturation during labour

To derive oxygen saturation by pulse oximetry (SpO2) values at each cervical dilation in labour in fetuses with normal neonatal outcome.

One hundred and forty-five women at term in established labour with ruptured membranes and cervical dilation at least 2 cm who had normal delivery outcome. The infants had 5 minute Apgar scores > or = 7, birthweight > or = 2500 g, umbilical cord artery pH > or = 7.15 and did not require assisted ventilation or admission to neonatal intensive care.

Women were monitored continuously with cardiotocography and fetal pulse oximetry using the Nellcor N-400 fetal pulse oximeter and FS-14 fetal oxisensor till delivery. Labour was managed according to established protocol without recourse to SpO2 readings.

There was a wide range of SpO2 values during labour in fetuses with normal outcome. Mean values averaged 50% +/- 10% throughout the first stage of labour, with lower ranges of SpO2 values above 30%. There was no significant difference in SpO2 readings at different cervical dilatations in the first stage of labour. Mean SpO2 values in the last 10 minutes before delivery were also not significantly different from those in the first stage of labour.

The range of SpO2 in 115 healthy fetuses during normal labour was wide, but always above 30%. There was no trend of SpO2 values in this study of 115 fetuses with normal neonatal outcome.