The safe balancing of maternal and neonatal benefits and risks in the second stage of labor has been hindered by a lack of high-quality, prospective evidence. Gimovsky and Berghella recently presented a well-conducted trial in which they randomized nulliparous subjects with epidurals to either the usual 3 hour second stage or to an extension of at least 1 hour.

They found a significant reduction in the cesarean delivery rate with extended time (relative risk, 0.45, 95% confidence interval, 0.22–0.93) and a corresponding increase in the number of vaginal deliveries. Maternal and neonatal outcomes were similar between the groups. Do these results indicate that we should adopt this policy as a form of primary prevention of the first cesarean delivery?

By reinterpreting the data in terms of prevented risk, one can determine the kind of public health impact that would be expected from wide implementation of such a policy. In this case the potentially harmful exposure is usual labor, so the prevented risk is calculated by subtracting the incidence in the unexposed group (ie, the intervention group) from the incidence in the exposed. The calculations would be as follows: prevented risk = exposed incidence – unexposed incidence = 16/37 – 8/41 = 0.237; prevented fraction = prevented risk/exposed incidence = (16/37 – 8/41)/(16/37) = 0.549.

For every 1000 patients exposed to extended labor, 237 cesarean deliveries would be prevented. The corresponding preventive fraction indicates that 54.9% of the expected cesarean deliveries in this population were prevented.

Overall, these results suggest that extended second-stage labor represents a promising approach for balancing maternal and fetal risks while working to reduce the rate of primary cesarean delivery. Before wider adoption, however, follow-up studies with larger sample sizes would be needed to appropriately address the study’s generalizability as well as the safety concerns, including the potential to unmask untoward outcomes that would have been prevented by cesarean delivery. It would be interesting to know whether these dramatic findings have led to a shift in the standard of care at the investigators’ home institution and whether any such larger studies are planned to shed light on these areas of uncertainty.