The effect of maternal body mass index on duration of induced labor.

The duration of active labor was associated with maternal BMI for underweight women and women with BMI ≥40 kg/m2 . Although women with BMI ≥40 kg/m2 who reached the active phase of labor had the same chance for a spontaneous vaginal delivery as normal weight women, the duration of active labor and the cesarean section rate were increased. The time from admission until start of active labor increased successively with maternal BMI.