The Natural History of the Normal First Stage of Labor

This article provides a summary of a landmark study on labor, in a large, multicenter modern cohort of women with singleton, vertex gestations. Emanuel Friedman published his original labor curve showing the expected progression of normal labor in 1955, and that for multiparous patients in 1956.2,3 He plotted the individual labor progression of 500 nulliparous laboring women from a single center to calculate the average progression of labor. In his cohort, 70% of whom were between 20 and 30 years old, many were Caucasian, and 55% of women were delivered via forceps. Dr. Friedman classically identified the second stage of labor starting at 4cm dilatation. Since the mid-20th century, many practice patterns have changed, and today’s population of women delivering in the United States is diverse and, on average, older and heavier than in 1955; therefore, use of the traditional labor curve has been questioned. The investigators in this study performed a secondary analysis of data from a multicenter cohort of 26,838 patients with singleton gestation, spontaneous labor, and normal outcomes. Using a sophisticated statistical approach Zhang et al. produced a modern labor curve.