Does oxytocin (Pitocin) augmentation of labor in women with epidural analgesia decrease the rate of operative deliveries, or neonatal and maternal morbidity?
Oxytocin augmentation does not reduce the frequency of cesarean delivery, instrumental vaginal delivery, or the combined outcome of both. Oxytocin also has no effect on low five-minute Apgar scores, postpartum hemorrhage, uterine hyperstimulation, or neonatal intensive care unit admission. (Strength of Recommendation: A, based on consistent, good-quality patient-oriented evidence.)
Many commonly practiced labor interventions aim to propel labor forward,1,2 based on the assumption that longer labor is associated with more maternal or neonatal complications. Evidence indicates that epidural analgesia prolongs the second stage of labor and increases the frequency of instrumental deliveries.3 Oxytocin augmentation of labor with epidural analgesia might then improve outcomes. But, does evidence support this assumption?
The authors searched the Cochrane Pregnancy and Childbirth Group's Trials Register and found two high-quality randomized controlled trials that addressed the topic. Both trials studied the effect of oxytocin augmentation on nulliparous women at different stages of labor. The first study randomized 226 fully dilated patients to oxytocin infusion (2 to 16 mU per minute) or saline.4 Oxytocin shortened the duration of the second stage of labor (134 vs. 151 minutes; P = .04) and increased the rate of rotational forceps deliveries (18% vs. 9%; P = .03), but did not affect the rate of nonrotational deliveries, overall forceps deliveries, cesarean deliveries, or fetal outcomes. The second study randomized 93 patients who were dilated to 6 cm or less to artificial rupture of membranes and oxytocin (2 to 32 mU per minute) or to saline infusion, and evaluated the same newborn outcomes as above.5 Oxytocin hastened completion of the first stage of labor (578 vs. 696 minutes; P < .05), but changed no other outcomes.
These data may have limited applicability to current U.S. practice because of the low rates of cesarean deliveries (3% and 16%) and the high rates of forceps deliveries (53% and 58%) in both trials.4,5 In 2010, the primary cesarean delivery rate in the United States was 23.6%.6 Currently, the rate of vacuum-assisted deliveries in the United States is about 3%, whereas the rate of forceps deliveries is 0.6%.1 On the other hand, doses of oxytocin in the two trials were the same as those used today.4,5
Although oxytocin augmentation of labor with epidural analgesia appears to modestly reduce labor duration, evidence does not show other clinical benefits. In addition, recent cohort studies have shown that our assumptions about the proper speed of labor should be tempered. Spontaneous yet healthy successful labor is slower and more variable than the Friedman curve taught in medical school.7 Augmentation of labor should thus be employed judiciously, keeping in mind the need to balance speed and diligence.