Other criteria should also be met. First, the latent phase should be completed, and the cervix is dilated ::4 cm. Also, a uterine contraction pattern of 200 Montevideo units or more in a 10-minute period has been present for 2 or more hours without cervical change. Rouse and associates (1999) challenged the "2-hour rule" on the grounds that a longer time, that is, at least 4 hours, is necessary before concluding that the active phase of labor has failed. We agree. The Consensus Committee (2016) has expanded the criteria, as described next.
Obstetric Care Consensus Committee. There are four recom mendations by the Consensus Committee (2016) applicable to management of the irst-stage labor. The irst admonishes against cesarean delivery in the latent phase of labor. Speciically, a prolonged latent phase is not an indication for cesarean delivery. This guideline is not new and is traceable to the work of Friedman (1954), on which traditional tenets are based.
The second directive, too, is conventional practice. It recommends against cesarean delivery if labor is progressive but slow-aprotraction disorder. This instance is typically managed with observation, assessment of uterine activity, and stimulation of contractions as needed.
A third instruction addresses the cervical dilation threshold that serves to herald active labor. Namely, a cervical dilation of 6 cm-not 4 cm-is now the recommended threshold. Thus, before this threshold, standards for active-phase progress should not be applied.
A fourth stipulation notes that cesarean delivery for activephase arrest "should be reserved for women at or beyond 6 cm of dilation with ruptured membranes who fail to progress despite 4 hours of adequate uterine activity, or at least 6 hours of oxytocin administration with inadequate contractions and no cervical change."
According to the Consensus Committee (2016), the "6-cm rule" stems from labor data from the Consortium on Safe Labor study (Zhang, 2010). This study derived its numbers from a retrospective observational dataset built from abstracted labor and delivery information from 19 hospitals across the United States. Various statistical methods and heavy manipulations of these numbers were used (Cohen, 2015b). As shown in Figure 23-2, a total of 62,415 women were analyzed after excluding all women with cesarean deliveries or asphyxiated newborns. The Consensus Committee (2016) was explicit that "the Consortium on Safe Labor data, rather than the standards proposed by Friedman should inform evidence-based labor management." Described in Chapter 21 (p. 432), the latter are labor curves that have been used since irst proposed by Friedman (1955).
Critics of the Consensus Committee (2016) recommendations note that the Consortium on Safe Labor data were derived from clinical settings with a net cesarean rate of 30 percent. hus, adherence to the new recommendations may fail to achieve desired cesarean rate reductions. Also, the study lacked a focus on neonatal safety, given that all the asphyxiated neonates were excluded. Supporters note that the study of prolonged first-stage labors by Cheng and coworkers (2010) found higher rates of cesarean delivery and chorioamnionitis but not higher rates of neonatal morbidity. However, Harper and associates (2014) analyzed maternal and neonatal adverse outcomes related to first-stage labor lengths. In 5030 women, first-stage labor durations were divided into those <90th percentile or those ::90th percentile, with incremental increases thereafter. These authors concluded that a longer irst-stage labor was associated with maternal and neonatal complications and that these should be balanced against the risks of cesarean delivery. his concern for adverse fetal and maternal efects resulting from the new Consensus Committee guidelines was echoed by Cohen and Friedman (2015a,b).