Figure 1.

Expected cumulative incidence (proportion) of spontaneous onset of labor by gestational age, according to fetal growth velocity (0 standard deviations (SDs), −2 SDs, or +2 SDs). A competing-risks model was used, with adjustment for the risks of labor onset due to premature rupture of the fetal membranes and elective delivery. The expected cumulative incidence curves were based on the following maternal characteristics: college graduation, average height (mean = 1.65 m), nulliparity, and no history of macrosomia at birth.