Contemporary Patterns of Spontaneous Labor With Normal Neonatal Outcomes

Abstract

Concepts developed several decades ago established criteria that defined labor arrest as no appreciable change in cervical dilation in the presence of adequate uterine contractions for more than 2 hours. However, these criteria may no longer be applicable to contemporary obstetric populations. The aim of this study was to examine contemporary labor patterns and estimate duration of labor in a large number of parturients with spontaneous onset of labor. Information on contemporary labor and delivery data in the United States was abstracted for the Consortium on Safe Labor, a multicenter, retrospective, observational study. The information was obtained from electronic medical records in 12 clinical centers. The study subjects were 62,415 parturients with a singleton term pregnancy who had spontaneous onset of labor, a vertex presentation, vaginal delivery, and normal neonatal outcomes. Average labor curves stratified by parity were constructed using a repeated-measures analysis. The duration of labor was estimated by an interval-censored regression stratified by cervical dilation at admission; the median and 95th percentiles were calculated to assess labor progression from 1 centimeter of dilation to the next. The data showed that at 4 cm, it may take more than 6 hours to progress to 5 cm, whereas it may take more than 3 hours to progress from 5 to 6 cm. The medians and 95th percentiles of duration of labor showed similar progression among nulliparous and multiparous women before 6 cm. After this point, however, multiparous women showed much faster acceleration of labor than nulliparous women. The 95th percentiles for the second stage of labor in nulliparous women with and without epidural analgesia were 3.6 and 2.8 hours, respectively. The investigators produced a partogram from the data for contemporary nulliparous women. These findings suggest that the use of 6 cm rather than 4 cm of cervical dilation as the start of the active phase may be more appropriate in the contemporary population. On the basis of these data, the investigators believe that the long-established definitions of normal and abnormal labor should be re-evaluated.