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12-04-2012 | Gynaecology | Article

Labor time has increased over past 50 years


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MedWire News: Women giving birth spend longer in labor today than their counterparts did 50 years ago.

Although the reasons for the increased time spent in labor are still unclear, changes in modern delivery practices could be the root cause, say Sarah Laughon (National Institutes of Health, Rockville, Maryland, USA) and team in the American Journal of Obstetrics and Gynecology.

They compared data on women who had term pregnancies and underwent spontaneous labor with cephalic singleton babies (n=39,491) from the Collaborative Perinatal Project between 1959 and 1966, with those from the Consortium on Safe Labor (n=98,359) who gave birth between 2002 and 2008.

Laughon and colleagues found that the increased time spent in labor in contemporary births was driven by an increased time spent in the first stage of the process. Indeed, they found that the first stage of labor has increased by 2.6 hours for first-time mothers. For women who have previously given birth, the time spent in the first stage of labor has increased by 2 hours.

Compared with women who gave birth between 1959 and 1966, those who gave birth half a century later were older, at 26.8 vs 24.1 years.

"Older mothers tend to take longer to give birth than do younger mothers," said Laughon in a press statement. "But when we take maternal age into account, it doesn't completely explain the difference in labor times."

Mothers who gave birth between 2002 and 2008 had a higher average pre-pregnancy body mass index (BMI; 24.6 vs 22.6 kg/m2), and a higher average BMI at delivery (29.9 vs 26.3 kg/m2) than those who gave birth 50 years ago. In addition, their babies weighed an average of 99 g more than those born 50 years ago.

Among changes in delivery practice over the 50 years, the researchers found that there has been a marked increase in epidural use, at 55% versus 4%. They note that epidural anesthesia is known to increase labor time, but that this did not account for all of the increase in labor time either.

Oxytocin administration was also more common in the modern-day pregnancies, at 31% versus 12%, respectively. As oxytocin is usually administered to speed up labor, Laughon explained, "without it, labor might even be longer in current obstetrics than what we found."

Other differences between the groups reflected changes in later-stage delivery practices, including a decline in the rate of episiotomy in modern-day practice (12 vs 68%) as well as the use of forceps (6 vs 40%).

In addition, Laughon et al found that the rate of cesarean delivery is four times higher today than it was 50 years ago.

After adjusting for maternal characteristics, labor was still significantly longer in the modern cohort than in the older cohort, "indicating that modern labor differs from the older cohort largely due to changes in obstetrics practices," write the authors.

"While we may not fully understand the factors contributing to longer labor, it is important to acknowledge that labor is longer in modern obstetrics and that routine interventions such as the use of oxytocin and timing of cesarean delivery may need to be thoughtfully reconsidered," they conclude.

By Piriya Mahendra

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