I. Risk factors that increase the risk of uterine rupture 1. Previous fundoplication or longitudinal uterine incision: Women with previous longitudinal uterine incisions, especially those who have undergone fundoplication, have a higher incidence of uterine rupture. This includes an inverted T- or J-shaped incision or a transverse incision extending the lower uterine segment to the upper uterine segment. The reported risk of uterine rupture after previous classic cesarean hysterotomy (fundoplication) ranges from 1% to 12%. A network study by the NIH Maternal-Fetal Medicine Section included nearly 46,000 women with singleton pregnancies who underwent TOLAC and found that the rate of uterine rupture in women with prior longitudinal incisions of the lower uterine segments was 2.0% compared to 0.7% in women with prior transverse incisions of the lower uterine segments. In recent decades it has been common to adopt a transverse incision of the lower uterine segment. 2. Induced labor: The incidence of uterine rupture was higher in induced women with a previous history of cesarean section than in women with a previous history of cesarean section but who had a spontaneous labor (1.5% vs. 0.8%). Because the risk of uterine rupture is so high with the use of prostaglandin analogs (2.45%), the American College of Obstetricians and Gynecologists has recommended against the use of misoprostol for induction of labor in women with a past history of cesarean delivery. Induction of labor with oxytocin alone also appears to slightly increase the risk of uterine rupture (1.1% risk of rupture), but this is not contraindicated. Data on the use of mechanical methods to promote cervical ripening in this population are limited to small samples and retrospective analyses, and the results are usually reassuring, but uterine rupture still occurs. 3. Prolonged labor: The incidence of uterine rupture is higher in women who have had a cesarean section and a repeat transvaginal delivery (TOLAC) than in women who have had an elective repeat cesarean section (ERCD).The 2010 NIH National Scientific Assembly statement showed that at full term, the incidence of uterine rupture was 0.78% in women with a TOLAC compared to 0.022% in women with an ERCD.The incidence of uterine rupture in women with an ERCD was 0.022% in women with a TOLAC. Lower Bishop scores on entry into the labor room and obstructed labor, especially when the uterine opening is significantly dilated (>7 cm), are factors that increase the risk of uterine rupture in women in labor. Slower dilatation during the first stage of labor and a longer second stage of labor also appear to increase the risk of uterine rupture. Risk factors that may increase the risk of uterine rupture 1. Increasing age of the mother, 2. Gestational age greater than 40 weeks, 3. Fetal birth weight greater than 4,000 g, 4. Delivery intervals of less than 18-24 months, 5. Single suture closure of the uterine incision, 6. Use of locking side sutures to close the uterus, and 7. Multiple previous cesarean deliveries. None of these risk factors are sufficiently reliable to help predict uterine rupture clinically. Factors that reduce the risk of uterine rupture The risk of uterine rupture is significantly reduced if a previous vaginal delivery precedes or follows a previous cesarean section.