Too close for comfort

The active phase of labor

The active phase of labor begins at various degrees of dilatation when the rate of dilatation transitions from the relatively flat slope of the latent phase to a more rapid slope. No diagnostic manifestations demarcate its onset, other than accelerating dilatation. It ends with apparent slowing of dilatation, a deceleration phase, which is usually short in duration and frequently undetected. Several aberrant labor patterns can be detected during the active phase, including protracted dilatation, arrest of dilatation, prolonged deceleration phase and failure of descent. Underlying factors may include cephalopelvic disproportion, excessive neuraxial block, poor uterine contractility, fetal malpositions, malpresentations, uterine infection, maternal obesity, advanced maternal age and previous cesarean delivery. When an active-phase disorder is identified, cesarean delivery is justifiable if there is compelling clinical evidence of disproportion. A prolonged deceleration disorder is strongly associated with disproportion and second stage abnormalities. Shoulder dystocia may occur if vaginal delivery eventuates. This review discusses several issues raised by the introduction of new clinical practice guidelines for labor management.

Extending the second stage of labor in nulliparous women with epidural analgesia: a cost-effectiveness analysis

The objective of this study was to evaluate maternal outcomes with an extended second stage of labor and determine if an extended second stage is cost effective. This theoretical model evaluated expectant management to 4 h compared to delivery at 3 h in the setting of a prolonged second stage of labor in nulliparous women with epidural analgesia. In our theoretical cohort of 165,000 women, we found that an extended second stage resulted in 53,268 more spontaneous vaginal deliveries, 14,163 fewer operative vaginal deliveries, and 39,105 fewer cesarean deliveries. This approach also resulted in 1 fewer instance of maternal death. An extended second stage, however, led to 14,025 more cases of chorioamnionitis, 1699 more episodes of postpartum hemorrhage requiring transfusion, and 119 more severe perineal lacerations, suggesting that while an extended second stage of labor results in overall improved maternal outcomes, there are tradeoffs. Expectant management to 4 h was the dominant strategy in the model, as it saved over $114 million US dollars and resulted in 4000 additional QALYs over our theoretical cohort. Sensitivity analysis indicated that expectant management until 4 h was cost-effective as long as the probability of cesarean delivery at 4 h was below 41.8%, and was the dominant strategy below 38.2% (baseline input: 19.5%). Multivariable sensitivity analysis demonstrated that the model was robust over a wide range of assumptions. Expectant management of the second stage of labor until 4 h is a cost-effective strategy to prevent primary cesarean deliveries, decrease costs, and improve some maternal outcomes, despite tradeoffs.

Second-stage labor: consensus versus science

There has been a recent significant evolution in suggested practices for the management of labor because of the increased national cesarean delivery rate. One of the most significant changes was promulgated by the 2014 Obstetric Care Consensus entitled, "Safe Prevention of Primary Cesarean Delivery," which recommended reconsideration of the upper limits of the length of labor in the second stage as well as the first stage. We previously published a 2016 Clinical Opinion challenging the second-stage practice change. Over the past 2 years, there have been at least 5 reports as well as 2 national organization statements supporting revised management of second-stage labor. We now revisit the second-stage issue because we believe that it is important to carefully clarify the current status resulting from consensus statements as well as the evolving current status of scientific evidence. We structured this Clinical Opinion using questions in an effort to chronicle the story of how obstetric precepts on second-stage labor in use for more than 50 years were being replaced. How did we get here? What is the current evidence? What can be learned from this experience? Should American obstetrics now "fall back" to pre-existing obstetric precepts for the management of second-stage labor after having "sprung forward" an additional hour-namely, lengthening the duration of acceptable second-stage labor to 4 hours as recommended by the Obstetric Care Consensus? We believe that the data published since our 2016 Clinical Opinion buttress our original position that prolongation of the second stage beyond historical precepts is unsafe.