Maternal hypoxaemia during labour and delivery: the influence of analgesia and effect on neonatal outcome.

The effect of analgesia on the incidence of hypoxaemia was assessed in an unrandomised trial in 51 parturients from the last hour of the first stage of labour until delivery. Women were retrospectively divided into four groups: no analgesia, pethidine with intermittent Entonox, extradural bupivacaine (either infusion of 0.125% or top-ups of 10 ml of 0.25%): and extradural infusion of 0.1% bupivacaine with 2 micrograms.ml-1 fentanyl. The lowest median incidence of desaturation (SpO2 < 94%) was in the extradural bupivacaine group: 0 min.h-1 in the last hour of the first stage and 0.1 min.h-1 in the second stage. The incidence was significantly lower than in the pethidine/Entonox group (1.4 min.h-1) in the last hour of the first stage (p < 0.001) and the extradural bupivacaine/fentanyl group (0.9 min.h-1) and no analgesia group (3 min.h-1) in the second stage (p < 0.05 in both cases). There was no correlation between maternal oxygenation during the second stage and measures of neonatal outcome including Apgar score and umbilical artery and vein blood gases.