Natural Childbirth after Previous Cesarean Delivery

What is the problem and what is known about it so far?
Many women would like to attempt vaginal birth in pregnancy following a prior cesarean delivery. The benefits of avoiding another surgical procedure must be weighed against the risks associated with labor after a prior cesarean delivery. While the most dangerous risk is rupture of the uterus during labor, other risks may include complications related to cesarean delivery after an unsuccessful trial of labor or harm to the infant.

Why did the researchers do this particular study?
The relative risks versus benefits of attempting a vaginal birth or choosing to undergo a repeat cesarean delivery are not known. Weighing the options will allow an individual to decide which is best for her.

Who was studied?
45,988 pregnant women who had undergone at least one prior cesarean delivery were included in this study. Each woman chose whether to have a repeat cesarean delivery or to attempt a vaginal birth. These women delivered at one of 19 large teaching hospitals in the United States.

How was the study done?
A registry of women with one prior cesarean delivery was developed at each hospital. Information about the patient and her current pregnancy were collected from all women who were more than 20 weeks pregnant at the time of delivery or who had delivered a baby weighing at least 500 grams (1 pound). Medical records were reviewed after delivery to look for complications in the mother or baby. Outcomes were compared between the mothers and babies who had elective surgery and the mothers and babies who tried vaginal birth.

What did the researchers find?
73% of women attempting to have a vaginal birth were successful; 17% of women attempting a vaginal birth needed a repeat cesarean delivery. More women attempting a vaginal birth developed a maternal complication (5.5%) compared to women who had an elective cesarean delivery (3.6%). These complications included infection, uterine rupture, or blood transfusion. Complications were more common in women that required cesarean delivery after a vaginal birth was attempted. The most serious complication was uterine rupture which occurred in 7 of 1000 deliveries when women attempted to delivery vaginally compared to zero when women had an elective cesarean delivery. The risk of uterine rupture was less when women went into labor spontaneously (4 per 1000) compared to when labor was induced (10 per 1000). Babies of mothers attempting a vaginal birth were more likely to suffer a brain injury, although the overall chances were low: 8 infants per 10,000 deliveries had brain injury in the group attempting labor compared to zero in the elective cesarean delivery group. The study did not find a difference in the rates of stillbirth or neonatal death between the two groups. The overall rate of complications in women who attempt vaginal delivery after prior cesarean birth is 1 in 2000.

What were the limitations of the study?
The women in this study chose their delivery method, so the risks observed were not from a random sample. Women who attempted vaginal delivery had different characteristics which may have affected the outcomes. Additionally, more women that had delivered vaginally in a pregnancy before their cesarean delivery attempted a vaginal birth. It is possible that only those women with the best chance of a successful vaginal birth underwent labor, making the success rate appear better.

What are the implications of the study?
Whether a woman will benefit from a trial of labor following a prior cesarean birth depends largely on the probability that she will have a successful vaginal delivery. Factors that can help in predicting success are a prior vaginal birth, spontaneous labor, or having a cesarean delivery in the past for reasons other than poor labor progress. Many women that attempt a vaginal birth will be successful. The risk of a poor outcome appears to be highest when labor is induced, especially if the cervix is not ready for labor. Health care providers can help a woman understand her personal chance of success with a trial of labor as well as the risks of multiple cesarean deliveries.

Summarized by Anna Benvenuto, College of Medicine, University of Vermont Summarized from "Maternal and perinatal outcomes associated with a trial of labor after prior cesarean delivery". Landon MB. New England Journal of Medicine. December 16, 2004. Volume 351, Number 25, pages 2581-2589.