Long Labor Doesn't Worsen Outcomes for Newborns

Karla Gale, MS

October 29, 2010

October 29, 2010 — Although a first stage of labor lasting more than 30 hours is linked to higher rates of cesarean delivery and chorioamnionitis, the newborns do well, according to an 18-year study.

Among more than 10,000 nulliparous women, those who labored between 3 and 30 hours had a c-section rate of 6.1%, versus 13.5% among those with longer labor. Rates of chorioamnionitis were 12.5% and 23.5%, respectively, although the researchers couldn't tell if the higher rate was a cause or an effect of prolonged labor.

But rates of 3rd- or 4th-degree perineal laceration, postpartum hemorrhage, and endomyometritis did not increase with duration of labor.

And infants born after 30 or more hours of labor were no more likely to suffer acidemia, sepsis, meconium aspiration, shoulder dystocia, or birth trauma, according to a report by Dr. Yvonne W. Cheng from the University of California, San Francisco, and her colleagues in the November issue of Obstetrics & Gynecology.

Their study included 10,661 term, cephalic, live singleton births to nulliparous women at UCSF between 1990 and 2008. They excluded deliveries involving induced labor, c-section for fetal indications during stage 1, and known lethal congenital anomalies. The authors note that active management of labor "was not a standard protocol" during the study period, with labor augmentation employed only for lack of progress.

The researchers stratified the length of the first stage of labor into three categories: lower than the 5th percentile (0-2.8 hours, n = 525), in the 5th-95th percentiles (2.8-30 hours, n = 9611), and above the 95th percentile (> 30 hours, n = 525).

They defined duration of the first stage of labor as the interval between labor onset to complete cervical dilation. Labor onset was determined by the presence of regular, painful uterine contractions at least every five minutes or three in a 10-minute period, and cervical change.

The median length of the first stage was 10.5 hours. Risk factors for increased duration of first stage were epidural analgesia, fetal occiput posterior position, and macrosomia.

Nearly three quarters of the cesarean deliveries were performed for arrest of dilation or descent. Half of the remainder were due to failed attempts at operative vaginal delivery, while the rest were due to indications such as cord prolapse, active bleeding, malpresentation and chorioamnionitis.

On multivariate analyses, the adjusted odds ratios were 2.28 for c-section and 1.58 for chorioamnionitis for those in labor for more than 30 hours versus a shorter duration.

"It is important to note," the authors say, "that although a prolonged first stage is associated with a higher risk of cesarean delivery, the majority of women still achieved vaginal delivery, even in those with a first stage of labor lasting beyond 30 hours." And it's possible, they add, that "the presence of chorioamnionitis may have caused dysfunctional contractions, which led to longer labor."

The adjusted odds ratio for admission to the neonatal intensive care unit was 1.53 for labor duration above the 95th percentile. However, the authors attribute this in part to more sepsis workups in the presence of chorioamnionitis, since the longest labor duration wasn't linked with any particular neonatal morbidity.

Dr. Cheng and her team point out that a vaginal delivery in the first pregnancy substantially decreases the risk of cesarean deliveries in later births. Therefore, they conclude, "management of labor should involve a thorough consideration of the ongoing risks of continued expectant management compared with the risks of intervention on the current and future pregnancies as well as the incorporation of patient preferences into the decision-making process."

Obstet Gynecol. 2010;116:1127-1135. Abstract

Reuters Health Information 2010. © 2010 Reuters Ltd.

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