Epidural analgesia and fetal head malposition at vaginal delivery

Objective: To determine if nulliparas who delivered with on-demand epidural analgesia are more likely to have malpositioning of the fetal vertex at de livery than women delivered during a period of restricted epidural use. Methods: A retrospective cohort of nulliparous women with spontaneous labor delivered during a 12-month period immediately before the availability of on-demand labor epidural analgesia was compared with a similar group of nul liparas delivered after labor epidural analgesia was available on request. The primary outcome variable was a non-occiput anterior position or malposi tioned fetal head at vaginal delivery. Results: The frequency of epidural use increased from 0.9% before epidural analgesia became available on demand to 82.9% afterward. Fetal head malposi tioning at vaginal delivery occurred in 26 of 434 (6.0%) women delivered in the before period compared with 29 of 511 (5.7%) in the after period (rela tive risk 0.95, 95% confidence interval 0.6, 1.6). No statistically signifi cant difference in the incidence of fetal head malpositioning was present a fter patients were stratified by mode of delivery (Mantel-Haenszel weighted relative risk 0.94, 95% confidence interval 0.6, 1.4). The study sample si ze provided 85% power to detect a two-fold increase in the incidence of fet al malpositioning from a baseline rate of 6% associated with on-demand epid ural use. Conclusion: Providing on-request labor epidural analgesia to nulliparas in spontaneous labor did not result in a clinically significant increase in th e frequency of fetal head malpositioning at vaginal delivery.