Press Release
December 14, 2004The risks from vaginal delivery after a prior Cesarean delivery are low, but are slightly higher than for a repeat Cesarean delivery. This finding is from the largest, most comprehensive study of its kind ever conducted, undertaken by the National Institute of Child Health and Human Development of the National Institutes of Health.
The study appears in the December 16 New England Journal of Medicine.
"These findings provide women who have had a Cesarean delivery — and their physicians — with reliable information to take into account when deciding whether to undergo labor or to have a repeat Cesarean delivery," said Duane Alexander, M.D., Director of the NICHD.
Among the complications the study found in women who attempted a vaginal birth after prior Cesarean delivery were rupture of the uterus, infection of the uterine lining, lack of oxygen to the infant brain, and infant death. The study authors noted, however, that the risks of these complications were very low.
Cesarean delivery consists of delivering a baby through an incision made in the abdominal wall and through the uterus, rather than through the vagina. Reasons for Cesarean delivery include failure of labor to proceed normally, fetal heart rate abnormalities, and complications involving the placenta. Because cesarean delivery is a major surgical procedure, it carries the risks posed by any other major surgery, such as infection or complications from the anesthetic. Having a Cesarean delivery may also complicate future births.
Uterine rupture is the most well known complication of attempted vaginal delivery after a prior Cesarean delivery. Uterine rupture occurs when the scar in the uterine muscle opens. The rupture may result in part or all of the baby and perhaps the placenta leaving the uterus, which may cause fetal heart rate abnormalities and perhaps fetal death. A more severe, or catastrophic, rupture may result in heavy bleeding, which can endanger the lives of both mother and baby. In some cases, the bleeding may be so severe that a hysterectomy must be performed.
However, repeat Cesarean delivery also may carry risks beyond those posed by delivering vaginally after a prior cesarean delivery, explained the NICHD author of the study, Catherine Spong, M.D., Chief of the Institute's Pregnancy and Perinatology Branch. The risk for infection and other surgical complications appear to be greater in women undergoing repeat cesarean delivery compared to those who are successful with a vaginal birth after Cesarean delivery.
Moreover, having a repeat cesarean delivery may complicate future pregnancies, sometimes causing the placenta to implant over the cervix, thereby interfering with the birth process. Prior Cesarean also increases the chances that the placenta will grow into the uterine wall, leading to difficulty with removal of the placenta after the birth. This may result in heavy bleeding during birth, perhaps leading to surgical removal of the uterus.
The decision of whether to attempt a vaginal delivery or to have a repeat Cesarean must be made carefully by women and their physicians. They must take into account, on the one hand, the risk of uterine rupture and its attendant complications, and balance these factors against the risk of surgical complications and the chances that repeat Cesarean delivery might complicate future pregnancies.
Citing figures compiled by the National Center for Health Statistics (NCHS), the study authors noted that the rate of Cesarean delivery had increased from 5 percent in 1970 to an all time high of 26 percent in 2002. Recent preliminary data released by the NCHS indicated an overall Cesarean delivery rate exceeding 27 percent for 2003. For the same period, the rate of vaginal birth after Cesarean delivery had fallen from 31 percent in 1998 to 10.6 percent in 2003. The U.S. Public Health Service, in its Healthy People 2010 Report, proposed a target rate of vaginal birth after Cesarean delivery of 37 percent.
The NICHD Maternal-Fetal Medicine Units Network researchers undertook the current study to more precisely estimate the risks from vaginal birth after Cesarean delivery as compared to having a repeat Cesarean delivery. Before the current study, the only information on this topic was from studies that reviewed discharge codes from hospital records, Dr. Spong said. Such analyses, undertaken after the fact, may fail to include important information about the birth. Moreover, the few studies that had been conducted generally didn't include a large enough number of women for a reliable calculation of the risks involved.
