NEW YORK (Reuters) -- Women who have an early epidural -- the spinal block anesthesia -- are almost 43 times as likely to be in labor for 12 hours or more, according to a report in the August issue of Obstetrics and Gynecology.
Other risk factors for a lengthy labor include less than two centimeters dilation of the cervix on admission, or when the baby weighs more than eight pounds.
The findings "suggest that early epidural placement and less-advanced cervical dilation on admission appear to be the most important predictors of prolonged labor," wrote lead study author Dr. Fergal Malone, of the Tufts University School of Medicine in Boston.
"We suggest that the incidence of prolonged labor might be reduced by delaying epidural placement until more advanced cervical dilation is achieved or until other methods of analgesia have proven adequate," say the study authors.
In the study of more than 9,000 women having their first child at The National Maternity Hospital in Dublin, 147, or 1.6%, had labor lasting 12 hours or more. About 65% of the time, the prolonged labor was caused by insufficient contractions of the uterus.
It is not clear why epidurals may increase the duration of delivery, according to the report. One recent study showed that anesthesia causes a slower rate of cervical dilation, an increased need for oxytocin -- the hormone that causes uterine contractions -- and a higher Cesarean delivery rate.
However, while the use of epidurals has increased from 10% to 60% at the Irish hospital since 1991, the number of women with prolonged labor has remained stable at 2%, Malone noted.
"This would suggest that it is not the presence or the epidural that predisposes a women to a prolonged labor, but the cervical dilation at the time of the epidural placement may be important," he concluded.
