Thirty-two percent of all births in the United States — nearly 1 in 3 — now occur by Caesarean section. The operations have been increasing steadily since 1996, setting records year after year, and have become the most common surgery in American hospitals. About 1.4 million Caesareans were performed in 2007, the latest year for which figures are available. The increases have caused debate and concern.
The concern arises because Caesareans pose a risk of surgical complications and research has found that they are more likely than normal births to cause problems that can put the mother back in the hospital and the infant in intensive care. Risks to the mother also increase with each subsequent Caesarean, because it raises the odds that the uterus will rupture in the next pregnancy, which can seriously harm both the mother and the baby.
Caesareans also increase the risk of dangerous abnormalities in the placenta during later pregnancies, which can cause hemorrhaging and lead to a hysterectomy. Repeated Caesareans can make it risky or even impossible to have a large family. In addition, costs for a Caesarean are nearly twice those for a vaginal delivery.
Most women who have had one or even two Caesareans can at least try to give birth vaginally, and studies have found that 60 to 80 percent succeed. But vaginal births after Caesarean sections have become increasingly uncommon.
Worries about the ever-increasing Caesarean rate led the National Institutes of Health to form a Consortium on Safe Labor, which performed a detailed analysis of electronic records from 228,668 births at 19 hospitals in the United States from 2002 to 2008. The study is the first to analyze how often Caesareans were performed before women went into labor (more than half the time) and how often after labor had begun.
The results were published this month by the American Journal of Obstetrics and Gynecology, and described in a telephone briefing by two of the authors, Dr. Jun Zhang and Dr. S. Katherine Laughon, from the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
Dr. Zhang said one thing that surprised him about the study was that a third of first-time mothers were having Caesareans. Although it was known that the overall Caesarean rate was 32 percent, some of that was thought to be due to repeat Caesareans.
The main reason for a Caesarean was a prior Caesarean. But in women who have not had Caesareans before, one factor that may increase the risk is the use of drugs to induce labor. The practice has been increasing, and the study found that induced labor, compared with spontaneous labor, was twice as likely to result in a Caesarean.
In the study, 44 percent of the women who were trying vaginal delivery had their labor induced. When Caesareans were done after induction, half were performed before the woman’s cervix had dilated to six centimeters, “suggesting that clinical impatience may play a role,” the authors wrote. Full dilation is 10 centimeters, and a Caesarean before six centimeters may be too soon, the researchers said.
Like other studies, this one found that few women were offered a chance to try vaginal birth after Caesarean.
“Physicians and patients may be less committed” to the vaginal births, the authors said.
Dr. Zhang said it appeared likely that the Caesarean rate in this country would keep increasing, though he said he hoped it would never match the rates in Brazil (70 percent) or China (60 percent). If there is any hope of reducing the rate in the United States, or at least slowing the increase, he and his colleagues said, the key is to lower the rate among first-time mothers and increase the rate of vaginal birth after Caesarean.