Research on the effects of epidural on the length of labor.affirms the common experience of midwives and nurses -- epidural anesthesia for childbirth frequently lengthens labor and is associate with increased rate of Cesarean surgery for "failure to progress" and fetal distress.

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NEW YORK (Reuters) -- Epidural analgesia to ease the pain of labor affects uterine performance and may increase the length of labor, Texas researchers report.

In an epidural, anesthetic is injected into the lower spine to block pain sensations from the lower body. Compared with women who received an intravenous drug to control labor pain, those who elected to receive an epidural were in labor longer and needed more medication to speed up their contractions, according to the article published in the March issue of the American Journal of Obstetrics and Gynecology.

Researchers led by Dr. James M. Alexander of the University of Texas Southwestern Medical Center in Dallas, studied 199 women with normal pregnancies who were admitted to the hospital with labor contractions. For all of the women, it was their first experience of labor. The women were offered a choice between an epidural injection for pain or intravenous Demerol. Women who elected to receive Demerol were given the additional option of switching to an epidural if pain relief was inadequate.

Women in both groups entered labor spontaneously, had similar degrees of cervical dilatation when pain medication was given and received equal dosages of oxytocin -- a drug given during labor to stimulate uterine contractions. However, the active first phase of labor, the duration of the second stage of labor (which includes delivery), and the time from admission to delivery were all significantly longer among women who received an epidural, the researchers report. A prolonged second stage of labor can weaken the muscles in the uterus necessary to push the infant out during delivery.

Of the 126 women who received an epidural, length of labor averaged nearly 8 hours, compared with approximately 6.5 hours among the 73 women who chose Demerol. The rate of fetal descent, which is the rate at which the fetus progresses to delivery, was also significantly prolonged (4.2 centimeters per hour with an epidural versus 7.9 centimeters per hour with Demerol).

But the study also showed that an epidural did not affect the health of the newborn. [ Editor's note: see article on increased admission to NICU for babies whose mother received epidural anesthesia] Mean birth weights of infants in both groups were almost identical, as was the health of the newborns and the rate of admission to intensive care.

This study adds to previous research suggesting that epidurals are associated with higher rates of cesarean section because prolonged labor can lead to fetal distress. The researchers recommend that women should be informed before they elect an epidural that it may significantly prolong their labor. And physicians may need to modify guidelines regarding the management of labor to recognize that an epidural can prolong labor. "Such modifications of labor expectations may serve to diminish the excess cesarean deliveries associated with epidural analgesia," they conclude.

SOURCE: American Journal of Obstetrics and Gynecology (1998;178:516-520)

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