Objective. To evaluate maternal and neonatal outcomes associated with birth at term by week of gestational age and also by onset of labor. Design. Cohort study. Setting. A state-wide perinatal outcome database. Population. 28 626 women with spontaneous onset of labor, induction of labor for recognized indications and induction of labor for non-recognized indications. Methods. Cohort study utilizing a validated dataset comparing outcomes with type of onset of labor using a log binomial model. Main outcome measures. Cesarean section, assisted vaginal birth, important measures of maternal and neonatal morbidity. Results. Induction of labor for non-recognized indications was associated with a significantly increased risk of a range of outcomes, including cesarean section (RR 1.67, 95%CI 1.55-1.80). The lowest risk of adverse maternal and infant outcome occurred with birth between 38 and 39 weeks and with the spontaneous onset of labor. Conclusions. Induction of labor for non-recognized indications at term is associated with an increased risk of adverse outcomes. Caution is warranted with a liberal policy of induction of labor at term in an otherwise uncomplicated pregnancy.