In a recent editorial Caughey addressed the optimal timing of intervention when the second stage of labor is long. He stressed that the duration norms drawn from Emanuel Friedman’s “notorious” research need reevaluation. Friedman, however, never advocated such use of durations as clinical norms. In fact, it was his enduring (and often corroborated) contribution that the feasibility of safe vaginal delivery is not determinable strictly from elapsed time in labor or contraction measurement, but is best realized by graphic analysis of dilatation and descent patterns.

Numerous factors, many elucidated by Friedman, affect second-stage duration, including fetal station at full dilatation, fetal position, uterine contractility, bearing-down efforts, pelvic architecture, epidural anesthesia, maternal body mass index, uterine infection, parity, and pushing style.

Most studies show the duration per se of the second stage has little influence on neonatal outcome, if the pattern of descent is normal and the fetus is properly monitored. This applies at least until 3 hours have elapsed, and probably longer. Risks of maternal hemorrhage and infection, and perhaps pelvic floor damage, however, are increased in long second stages, reasons to avoid its unnecessary prolongation.

Just as the pattern (slope) of dilatation of active labor best defines normal progress in the first stage, so should the pattern (slope) of descent and not its duration be the basis for decisions about intervention in the second stage. The key to management resides in determining whether and how the pattern of descent deviates from normal. When it does, it can then be determined what the cause of that divergence is, and whether it can be safely overcome.

It is quite possible for the pattern of descent to be normal and for the second stage to exceed 2 or even 3 hours. Consider a nullipara’s second stage beginning at 0 station with steady descent at 1.5 cm/h. The head would safely reach the pelvic floor in 3 hours. By contrast, the likelihood of a safe vaginal delivery would be much reduced if there were no descent after only 1 hour, especially with fetal macrosomia or pelvic contraction present. In that situation additional counterproductive hours of labor might increase the risk of harm to both mother and fetus.

Defining the permissible duration of the second stage should be individualized, based on the identification of graphically definable disorders of descent combined with other clinical observations to predict the probability of safe vaginal delivery.