Contrary to what had previously been reported, epidural analgesia, used to relieve women's pain during labor, does not appear to increase a woman's chances of having a Cesarean section, according to an analysis of hospital records by researchers at the National Institute of Child Health and Human Development (NICHD) and Tripler Army Medical Center, in Hawaii.
The researchers also found that epidural analgesia, or pain relief, does not increase the chances for difficult birth, as many had feared, but does prolong labor by an average of 25 minutes. The findings appear in the July (current) issue of the American Journal of Obstetrics and Gynecology. "The decision to receive epidural analgesia is a highly individual choice faced by women and their physicians," said Duane Alexander, M.D., Director of the NICHD. "The results of this study provide additional information for pregnant women and their physicians to use in making this important decision."
More than 50 percent of pregnant women in the U.S. receive epidural analgesia to relieve the pain of labor, said the study's principal investigator, Dr. Jun (Jim) Zhang, Ph.D., M.D., of NICHD's Division of Epidemiology, Statistics and Prevention Research. The procedure involves using a needle to inject a pain reliever into a space next to the spinal cord in the lower back. Many obstetricians have been concerned that the procedure may also slow down labor and thus increase the chances that a woman in labor may need a cesarean section.
The researchers began by examining the labor records from the Tripler Army Medical Center. In late 1993, the U.S. Department of Defense required that epidural analgesia be made available to women in labor at military medical centers. As a result, the rate at which first time mothers received epidural analgesia at the medical center increased from 1 percent to 84 percent. During that time, there were no major staffing changes at the hospital and no change in delivery procedures.
"This unique natural experiment offers an ideal opportunity to study the impact of epidural analgesia on the course of labor and delivery," the researchers wrote.
For the study, the researchers analyzed the records of two groups of first-time mothers: those who gave birth in the 12 months before October 1, 1993, designated the "before period" and those who gave birth in the 12 months after October 1, 1995, the "after" group. In all, there were 507 women in the "before" group and 581 women in the "after" group.
The researchers found that there was no difference in the rate of Cesarean section between the before and after groups. Nor was there a difference in the incidence of difficult vaginal births requiring forceps or vacuum instruments. On average, however, the women in the after group experienced an increase in labor duration of 25 minutes as compared to the before group. The increase in labor duration was confined to the second stage of labor, from the time when the woman's cervix is completely dilated until the baby is actively expelled from the birth canal. The length of the first stage of labor, during which the cervix dilates, did not differ between the two groups.
Dr. Zhang said that this prolongation of labor did not appear to have a negative impact on either mothers or infants.
The two groups also differed in the timing of when their infants required assistance from medical instruments. The need for use of forceps or vacuum extraction to assist the baby through the birth canal appeared later in the after group than in the before group. Dr. Zhang explained that, in the before group, these extraction procedures were more often used when the baby was higher up in the birth canal. For the after group, the procedures were used when the baby was much farther along in the birth canal.
This shift in the timing of the procedures meant that, in general, less force was needed for the after group to aid in the delivery of the infant from the birth canal. Dr. Zhang explained that this translates into a reduced risk for infants and mothers needing the extraction procedure. Extraction by forceps carries a slight risk of injury to the muscles surrounding the birth canal and temporary bruising or nerve damage to the infant's face. Vacuum extraction carries a small risk of bleeding or bruising on the infant's scalp.
The researchers concluded that their findings indicated that labor epidural analgesia does not increase the likelihood of cesarean delivery. "The length of active phase of labor appeared unchanged; however, labor epidural analgesia likely prolongs the second stage of labor."
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