Epidural anesthesia lengthens the second stage of labor, the one in which women push. But a study published on Wednesdayhas found that epidurals are associated with an even longer duration in the second stage than is generally recognized, suggesting that some women may be subject to unnecessary interventions by doctors who wrongly fear labor has become prolonged.
The finding indicates that “clinicians might need to wait later before intervening with oxytocin, forceps, vacuum or a cesarean,” said Dr. S. Katherine Laughon, an investigator at the National Institutes of Health who was not involved in the study, which was published in Obstetrics and Gynecology. Still, she added, “clinicians and women need to balance benefits of vaginal delivery with potential increases in risk for mom and baby.”
Current guidelines by the American Congress of Obstetricians and Gynecologists, or ACOG, define an abnormally long second stage as more than three hours for women who received an epidural and are giving birth for the first time, and more than two hours for first births without an epidural.
The new study suggests a normal second stage can take as long as 5.6 hours for women who get epidurals during their first births, and as long as 3.3 hours for those who do not get epidurals.
For women who have given birth previously, the group’s guidelines define an unusually long second stage as two hours with an epidural, one hour without. The new study found that the second stage for these women can be as long as 4.25 hours and 1.35 hours, respectively.
“This paper is very important, and ACOG needs to update its 2003 guidelines,” said Dr. Robert L. Barbieri, chairman of obstetrics and gynecology at Brigham and Women’s in Boston, who was not involved in the new study. He added, “I will change my practice and feel more comfortable going to five and a half hours with a first birth after an epidural with reassuring fetal monitoring.”
Researchers at the University of California, San Francisco, analyzed the records of 42,268 women who delivered vaginally without problems between 1976 and 2008. Roughly half had epidurals.
The investigators compared the average length of the second stage of labor among women who had epidurals with that among women who did not. They also compared the upper limits of duration for both groups.
Thirty-one percent of first births and 19 percent of subsequent labors would have been classified as abnormally long by the current ACOG definition, the researchers found.
“It’s time to re-examine what normal and abnormal is, and revise our guidelines based on modern obstetric population,” said Dr. Yvonne W. Cheng, the lead author of the study and an associate professor of obstetrics and gynecology at the University of California, San Francisco.
The research is part of a growing body of evidence suggesting that a normal second stage of labor is now longer than it was decades ago. In 2010, a study of more than 62,000 women found it was as long as 3.6 hours for first-time mothers after an epidural, and 2.8 hours for women who did not get one.
A 2012 summary of a joint meeting of ACOG and the National Institutes of Health concluded that adequate time for each labor stage “appears to be longer than traditionally estimated.” For the second stage, it is closer to four hours for first-time mothers who had epidurals, and three hours for those who did not.
But this latest study is the first to suggest such an extended second stage may be ordinary.
“One of the messages of this study is, sit on your hands a little longer, don’t rush into an instrumental vaginal delivery or a cesarean, because really everything could be fine,” said Dr. Barbara Leighton, a professor of anesthesiology at Washington University in St. Louis School of Medicine, who has researched the effects of epidurals on labor.
But while Dr. Leighton supports revising ACOG recommendations, she believes that the current study did not prove that longer labor is caused by epidural anesthesia. Women who request anesthesia may be predisposed to longer labor for other reasons, she said.
Dr. Jeffrey Ecker, the chairman of the committee on obstetrics practice for ACOG, said today’s clinicians are “increasingly recognizing there can be healthy outcomes and vaginal deliveries of healthy babies when the second stage extends beyond how it’s traditionally been defined.”
He added, “Often what’s best and most appropriate — and most difficult — during labor is patience.” He would not say whether a revision of guidelines is in the works.
Patience during labor is not risk-free. The new study found that babies are more likely to have birth trauma, such as a bruise on the head or a clavicle fracture, after longer second-stage labor. But these infants did not have lower scores on tests designed to measure physical health in newborns, nor did they experience more admissions to intensive care.
The risks of significant perineal lacerations and postpartum hemorrhage were higher in women who experienced prolonged second-stage labor, both by ACOG’s definition and by the upper limits of the study’s definition of normal.
While Dr. Laughon applauded the large number of participants in the study, she cautioned that “they are saying we should wait longer, but we still don’t know if that’s safe.”
A lot has changed since the 1950s, when labor progression norms were established. Back then, more babies were delivered by forceps and continuous fetal monitoring was not used.
“We are doing less interventions to facilitate a shorter second stage, and we’re letting the power of the uterus and a mother’s pushing determine the length of the second stage,” Dr. Barbieri said.