Post-cesarean delivery dilemma: to cesarean again, or not?

November 19, 2000

Study shows little difference in risk between elective repeat cesarean, and labor with vaginal birth among women who had cesarean before

Ann Arbor, MI - The old adage "once a cesarean, always a cesarean," has met with significant controversy over the years.

At some points in history, many doctors were recommending that women who'd had previous cesarean deliveries consider vaginal birth; at other times, another cesarean. This polarization has left some women questioning what's best for them and their babies.

But a new study by University of Michigan and University of Toronto researchers published today in the American Journal of Obstetrics and Gynecology suggests that low-risk women shouldn't agonize so much over the decision. This finding comes from an exhaustive review of recent studies on the topic.

"For those women who have had previous cesarean births, a trial of labor, or intended vaginal birth, has significant benefits for the mother," says Ellen Mozurkewich, M.D., a fellow in the Division of Maternal-Fetal Medicine in the U-M Health System, and principal investigator on the study.

"A trial of labor may cause a slight increased risk to the fetus or neonate, but the absolute risk of death or serious morbidity is quite low."

When a woman undergoes a cesarean delivery, an incision is made in the uterus. The primary concern for these women in subsequent births is to make sure the scar that remains from the previous cesarean does not come apart during labor or vaginal birth.

"This study was motivated by growing controversy over a question that we had believed to be settled," Mozurkewich says.

The study explains that as cesarean delivery become safer in the 1970s and 80s, doctors recommended it more and more. The rate of cesarean deliveries peaked in 1988 at 24.7 percent, the study notes.

Data published in the 1980s and early 1990s detailed the relative safety of vaginal birth for women who'd had previous cesareans. The data concluded that both mother and baby benefited from the vaginal birth. In response to these findings, the rate of vaginal birth after cesarean rose, increasing by 50 percent between 1989 and 1996.

Unfortunately, the rate of uterine ruptures and rupture-related neonatal morbidity and mortality also increased during that period and several high profile legal claims caused a return to the "once a cesarean, always a cesarean" mindset among some patients and practitioners.

Since those publications, Mozurkewich said the vaginal birth after cesarean rate has fallen by 7 percent from 1996 to 1998 and the rate of cesarean delivery overall increased to 21.2 percent in 1998.

Mozurkewich's goal was to use a meta-analysis to compute the most recent available estimates of morbidity and mortality rates for mothers and babies associated with trial of labor compared to elective repeat cesarean delivery.

She and co-author Eileen Hutton, MNSc., a registered midwife who is studying for a doctoral degree at the University of Toronto, examined and pooled data from 15 previous studies involving a total of nearly 48,000 women.

The study compares women who labored - even those that eventually ended in cesarean - with those who chose to have elective cesarean deliveries without labor.

They found that the strain of labor and vaginal delivery may indeed result in small increases in the uterine rupture rate and in fetal and neonatal morbidity rates when compared to elective repeat cesarean delivery. But their data also revealed that maternal fevers and the need for transfusion or hysterectomy might be reduced with vaginal delivery, she said.

"There seem to be significant benefits to the mother from trial of labor," Mozurkewich says. "But there may also be a small, increased risk to the baby from trial of labor," she adds.

Mozurkewich adds a caution to her results. The data used in the meta-analysis were based on studies that were not randomized, meaning women were able to choose, with their doctor's guidance, whether to give birth vaginally or through cesarean. This choice often includes some bias, she said.

Future studies may allow a randomized trial in which low risk women would be assigned at random to have one delivery plan or the other, removing that bias, Mozurkewich says.

For now, she says the bottom line is that, although it is not always possible for doctors to determine which women are most likely to have complications in either form of delivery, it's important for women to discuss the risks and benefits of both options with the doctor.

University of Michigan Health System

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