A comparison of the effect of extradural and parenteral analgesia on maternal plasma cortisol concentrations during labour and the puerperium.

Maternal plasma levels of cortisol were measured serially by radioimmunoassay in two groups of 12 patients during induced labour and in the puerperium. One group was given continuous extradural analgesia throughout labour, the other group received pethidine and promazine in response to pain. Pre-induction cortisol levels were significantly higher in patients who were to have extradural analgesia but the percentage increase in plasma cortisol during labour was considerably less than in patients with parenteral analgesia; in second stage labour, mean cortisol levels were the same in the two groups. This study suggests that patients who had chosen to have extradural analgesia may have been more anxious before labour than the other patients but continuous, extradural analgesia suppressed to some extent the percentage increase in mean cortisol levels found during labour in patients given parenteral analgesia. In the puerperium, there was no difference in mean cortisol levels in the two groups.