The effect of epidural opioids on maternal oxygenation during labour and delivery.

The effects of epidural fentanyl on the incidence of maternal hypoxaemia during labour and on neonatal welfare were examined. Women were randomly allocated to receive one of two epidural infusions, bupivacaine 0.125% alone or bupivacaine 0.0625% with 2.5 micrograms.ml-1 fentanyl, and maternal arterial oxygen saturation was monitored continuously until delivery. The median incidence of desaturation (SpO2 < 95%) during the active phase of the second stage of labour was significantly greater in the fentanyl group than in controls (2.9 versus 0.6 min.h-1, p = 0.02). Similarly, the incidence of desaturation to SpO2 < or = 90% was greater in the fentanyl group than in controls (p = 0.02). There was no correlation between maternal oxygenation or plasma fentanyl concentration and neonatal welfare as measured by umbilical arterial and venous blood gas and acid base status, Apgar score and Neurologic and Adaptive Capacity Score.