Comparison of the maternal and fetal effects associated with intermittent or continuous infusion of extradural analgesia.

Eighty normal primigravidae received an extradural dose of 0.25% bupivacaine and were then allocated randomly to receive "top-ups" of 0.25% bupivacaine (group A) or an infusion of 0.125% bupivacaine (group B). Group B received supplementary top-ups if required. Group A required more top-ups (147 vs 80) (P < 0.01). No maternal advantage was demonstrated from each regimen. Fetal state was assessed by analysis of the cardiotocograph during labour and the condition of the fetus at delivery. Three different patterns of late deceleratory episodes were identified (grades 1-3). Total numbers of episodes per group were similar (group A, 71; group B, 69). More episodes in group A were related to top-ups (42/71 vs 18/69; P < 0.01) but the incidence of episodes after a top-up was similar (group A, 42/147 (28.6%); group B, 18/80 (22.5%)). In group A, 31/42 events (73.8%) were transient compared with 11/18 persistent episodes (61.1%) (> 10 min duration) in group B. However, the difference in the deceleratory patterns did not influence the condition of the fetuses at delivery.