These authors provide options to these times before cesarean deliv ery is performed. Namely, longer durations may be appropriate as long as progress is documented. Also, a specific maximal length of undergo operative delivery has not been identiied.
Intuitively, the goal to lower cesarean delivery rates is best balanced with one to ensure neonatal safety. And, it is problematic that no robust data on neonatal outcomes support the safety of allowing prolonged second-stage labor. Data from many evaluations reveal that serious newborn consequences attend second-stage labors longer than 3 hours (Allen, 2009; Bleich, 2012; Laughon, 2014; Leveno, 2016; Rosenbloom, 2017). Other data, when adjusted for labor variables, show no diference in neonatal complications for these longer second stages (Cheng, 2004; Le Ray, 2009; Rouse, 2009). Grobman and colleagues (2016) have argued that the absolute number of such adverse outcomes is small and "overall outcomes remain good." That said, some of the complications are severe. Thus, to fully ascertain specific efect of these guidelines on morbidity rates, randomized controlled trials are needed.
It is possible that prolonged first-stage labor presages that with the second stage. Nelson and associates (2013) studied the relationships between the lengths of the irst and second stages of labor in 12,523 nulliparas at term delivered at Parkland Hospital. The second stage signiicantly lengthened concomitantly with increasing irst-stage duration. The 95th percentile was 15.6 and 2.9 hours for the first and second stages, respectively. Women with irst stages lasting longer than 15.6 hours (>95th percetile) had a 16-percent rate of second-stage labor lasting 3 hours (95th percentile). his compared with a 4.5-percent rate of prolonged second stages in women with irst-stage labors lasting <95th percentile.
With full cervical dilation, most women cannot resist the urge to "bear down" or "push" each time the uterus contracts (Chap. 22, p. 438). The combined force created by contractions of the uterus and abdominal musculature propels the fetus downward. At times, force created by abdominal musculature is compromised suiciently to slow or even prevent spontaneous vaginal delivery. Heavy sedation or regional analgesia may reduce the reflex urge to push and may impair the ability to contract abdominal muscles efectively. In other instances, the inherent urge to push is overridden by the intense pain created by bearing down. Two approaches to second-stage pushing in women with epidural analgesia have yielded contradictory results. The irst advocates pushing forcefully with contractions after complete dilation, regardless of the urge to push. With the second, analgesia inusion is stopped and pushing begins only ater the woman regains the sensory urge to bear down. Fraser and coworkers (2000) found that delayed pushing reduced diicult operative deliveries, whereas Manyonda and associates (1990) reported the opposite. Hansen and colleagues (2002) randomly assigned 252 women with epidural analgesia to one of the two approaches. No adverse maternal or neonatal outcomes were linked to delayed pushing despite signiicantly prolonging second-stage labor. Plunkett and coworkers (2003), in a similar study, confirmed these indings.