From University of Texas Southwestern Medical Center at Dallas
Labor induction in overdue pregnancies does not lead to more caesarean sections, study shows
DALLAS - May 31, 2001 - Researchers at UT Southwestern Medical Center at Dallas have shown that labor induction alone does not increase the probability of Caesarean section in pregnant women who exceed their due date.
The rate of labor induction in the United States has increased steadily since 1989. Currently about one in five women undergo labor induction, with the highest rates occurring in women who are at least one week past their due dates (at least 41 weeks gestation).
In an article published today in the Journal of Obstetrics and Gynecology, Dr. James Alexander, assistant professor of obstetrics and gynecology at UT Southwestern, and his colleagues report that Caesarean deliveries were, in fact, increased in patients whose labors were induced, but this was due to risk factors intrinsic to the patient, rather than to labor induction itself. Correcting for risk factors like first-time pregnancy, undilated cervix prior to induction and epidural analgesia, the physicians concluded that these circumstances, not induction of labor per se, accounted for the increase in Caesarean deliveries.
Physicians examined 1,325 women in a special post-term clinic at Parkland Memorial Hospital between Dec. 1, 1997, and April 4, 2000. These women had reached 41 weeks gestation and were scheduled for induction of labor at 42 weeks.
"We studied a group of women whose pregnancies extended beyond their due date and who were scheduled for induction of labor," Alexander said. "We found that inducing labor resulted in more Caesarean deliveries in women who were not fully dilated and in those who were experiencing their first pregnancy."
The Caesarean delivery rates were compared to those who entered spontaneous labor (52 percent) and those who underwent induction. Women with diabetes, prior Caesarean delivery, multiple fetuses, breach presentation or other medical or obstetric problems were excluded from the study.
In the spontaneous labor group, 14 percent of the women underwent Caesarean section. In those whose labor was induced, 19 percent delivered by Caesarean.
"Patients' failure to progress resulted in a higher percentage of Caesarean deliveries in the induced group," Alexander said. "However, the risk factors intrinsic to the patients - rather than the labor induction itself - resulted in an excess of Caesarean deliveries in the women we studied."
Other findings showed that labor was longer and more likely to extend over 10 hours in women who were induced. The average labor time for spontaneous labors was less than six hours.
Dr. Donald McIntire, assistant professor of obstetrics and gynecology, and Dr. Kenneth Leveno, professor of obstetrics and gynecology at UT Southwestern, also participated in the study.