Weight status is an important determinant of many health indices. Data from a clinical trial on measures to lower genital tract trauma in vaginal birth were used for a secondary analysis. The goal was to describe the relationship of body mass index and pregnancy weight gain to clinical intrapartum care, infant birthweight, and genital tract trauma with vaginal birth. Intrapartum care measures and labor events did not vary by maternal weight status. Overweight and obese women were more likely to be parous, and Hispanic or American Indian. Total pregnancy weight gain decreased, and infant birthweight increased as body mass index category increased. Obese women who gained 40 or more pounds during pregnancy had elevated rates of macrosomia and genital tract lacerations.