The findings suggest that the long-held practice of reducing or stopping an epidural in the later stages of labor could be “out of date and misguided,” said the report in the journal Obstetrics and Gynecology.
Epidurals, which deliver pain-numbing medications close to the nerves of the spine via catheter, have been widely used since the 1970s.
For the study, 400 women agreed to receive an epidural early in labor and then be randomly assigned to have that painkiller continued throughout the later part of labor, or exchanged with a saline placebo without their knowledge.
Neither the women, researchers, doctors or midwives knew what was in the catheter-delivered infusions — a study design known as “double-blind” which tends to enhance reliability and avoid bias.
The second stage of labor begins when the cervix is completely dilated and ends when the baby is delivered.
When this stage of labor runs long, adverse outcomes — including harm to the fetus — are more common.
To avoid complications, obstetricians routinely discontinue the epidural at this stage.
But the results of the study showed that epidural or not, labor lasted just about as long. All the women in the study were healthy, first-time mothers.
The duration of labor averaged 52 minutes for women given active pain medication versus about 51 minutes for women given the saline, just a 3.3 percent difference, said the report.
“We found that exchanging the epidural anesthetic with a saline placebo made no difference in the duration of the second stage of labor,” said senior author Philip Hess, director of obstetric anesthesia at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School.
Nor did epidural medication have any effect on the health of the newborn babies, the normal vaginal delivery rate, the position of the fetus at birth or any other measure of fetal well-being, said the report.
During the study, obstetricians asked to stop epidural infusions in 38 of the 400 patients because their labor was progressing poorly.
Seventeen of these women were in the saline group, while only a slightly higher number — 21 — were in the active medication group.
As expected, the women whose drugs were halted experienced increasing levels of pain as labor went on.
“Twice as many women given the placebo reported lower satisfaction with their pain relief compared to those provided the anesthetic,” said Hess, calling for more research into the matter.
“We didn’t see any negative effects, but epidural analgesia in the second stage of labor remains controversial and merits follow up studies.”