Now, a new meta-analysis of 16 studies challenges that thinking, with evidence that a Caesarean may not be necessary if labor is induced in pregnancies that go beyond the normal nine months.
"Intuitively, we have always thought that because inducing labor before 41 weeks resulted in a higher rate of Caesarean delivery, that inducing at 41 weeks would have the same effect. But we were very surprised to find the opposite was true," says study author Dr. Luis Sanchez-Ramos, a professor of obstetrics and gynecology at the University of Florida in Jacksonville.
The new research appears in the June issue of Obstetrics and Gynecology.
When compared to labor management -- a process of wait-and-see -- inducing labor on or near a woman's due date was less likely to lead to a Caesarean delivery than if doctors simply let nature take its course, Sanchez-Ramos says.
"We think that perhaps something occurs during the waiting period that results in problems that ultimately end up requiring a Caesarean-section birth, whereas inducing labor seems to help avoid some of those problems and consequently reduces the need for a Caesarean section," Sanchez-Ramos says.
But critics of the study charge the difference in the number of women involved in the research who required Caesareans was small, and the method of analysis used to obtain the information might be flawed.
"Based on this review, I don't believe there is enough evidence to create a hard-and-fast rule about inducing labor," says Dr. Steve Goldstein, a professor of obstetrics and gynecology at New York University Medical Center. "The difference in Caesarean rates was small, and the method of review can easily omit specific information on each pregnancy that might definitely influence the outcome."
The best approach, Goldstein says, is to treat every pregnant woman on an individual basis.
"I certainly would not change the way I deal with my overdue patients based on this study," he says.
Sanchez-Ramos says his findings back up conclusions of a large Canadian-based study that found similar results.
"I believe the difference in Caesarean section rates is significant and that these findings should change our way of thinking about labor induction in women who are past due," he says.
The meta-analysis -- a systematic review of literature on induced labor -- took into account 16 studies on labor induction published between 1969 and 1992. This included one large Canadian study of some 1,900 women, bringing the total number of patients included in all the research to 6,588. All of the women were pregnant for at least 41 weeks, and considered to be at least one week past their due date.
The result: When compared to women whose doctors took a wait-and-see approach, those women who had labor induction had a 2 percent lower rate of Caesarean-section delivery. What's more, the babies of these women had a lower prenatal mortality rate, though the researchers believe the difference was not statistically significant.
"Overall, the studies show that inducing labor in women who are past due can result in fewer Caesarean sections, and it's something that doctors should consider when making labor-management decisions," Sanchez-Ramos says.
In a second study also published in the June issue of Obstetrics and Gynecology, doctors from the University of Texas Medical Branch at Galveston report on a new procedure known as transabdominal uterine electromyography. When administered on or near a due date, it can predict whether labor will start within the next 24 hours.
For women at risk of a premature delivery, it can predict whether labor will begin within four days.
The test, which measures how a muscle fiber responds to electrical nerve stimulation, was used to calculate the electrical activity of the uterus, which grows more robust as delivery time draws near. By watching for peaks in the electrical activity, doctors were able to predict delivery times with surprising accuracy, the study says.
The test can be used to more accurately evaluate preparedness for labor, the researchers say. It can also be used to prevent unnecessary hospital admissions and improve perinatal outcomes, including prevention of pre-term labor and better use of labor-inducing medications.