Mothers who have had a Caesarean section increase their chances of rupturing their uterus if they attempt vaginal delivery during their next pregnancy, especially if labor is induced, according to a new study.
For years, doctors advised women who had Caesarean sections to deliver all their babies by C-section because of the scars left on their uterus. But more recently, women have been encouraged to attempt to deliver vaginally after a Caesarean and approximately 60 percent of them try labor.
From 1989 to 1996, the rate of vaginal births after a Caesarean increased 50 percent in the United States to 28 per 100 women. By 1999, it was down to 23 per 100 women.
The rate of Caesarean births has remained at about 22 percent during the same 10-year period.
Questions persist, however, about whether labor causes problems such as uterine rupture, an uncommon but serious complication. A tear in the uterus can result in a hysterectomy, blood transfusions or death for the mother and brain damage or death for the infant.
Researchers at the University of Washington in Seattle studied this issue by looking at 20,095 women who delivered their first baby by Caesarean section and then had a second child. There were 91 cases of uterine rupture, according to the findings reported in Thursday's New England Journal of Medicine.
Compared to women in the group who had a repeat C-section without labor, the researchers said those who went into labor spontaneously were three times more likely to have a uterine rupture. Women whose labor was induced _ but not with a class of drug known as prostaglandins _ were nearly five times more likely to have a rupture and those induced with a prostaglandin, which is more potent, were 15 times more likely.
``By no means does our study suggest that no woman should have a vaginal birth after a Caesarean. What it says is there are risks of doing that that we didn't fully appreciate,'' said one of the researchers, Dr. Thomas R. Easterling.
He said some women may opt to try a vaginal delivery for the birth experience or because of the faster recovery. Those who try labor should do it in a hospital that can quickly perform a C-section should it become necessary, he said.
``Women need to talk to their provider about their own individual pregnancy and their health,'' said Mona Lydon-Rochelle, another researcher. ``They may have a very low chance of uterine rupture'' and the benefits may outweigh the risks.
The data on the 20,095 women was culled from birth certificates and hospital discharge records in the state of Washington from 1987 to 1996. Home births were not included.
``It's a huge study and it shows quite clearly that there is an increased risk associated with the use of prostaglandins,'' said Dr. Michael F. Greene, who wrote an editorial accompanying the study and is director of maternal-fetal medicine at Massachusetts General Hospital in Boston.
He said doctors need to tell patients about the risk of uterine rupture so they can weigh the risks and the benefits of a vaginal birth.
``Strictly speaking, if the question you're asking is, 'What is safest for the fetus?' There's no doubt repeat Caesarean is safest,'' Greene said.