Convinced that you spent a lot more time in labor with your baby than your mom did with you?
You may have.
According to new research from the National Institutes of Health, moms take significantly longer to give birth today than they did 50 years ago.
The study, published online in the American Journal of Obstetrics and Gynecology, compares data from tens of thousands of women in the late 1950s through the mid '60s with nearly 100,000 women between 2002 and 2008.
First-time moms in the latter group spent two-and-a-half more hours in the first stage of labor, the period of time it took them to go from 4 centimeters to fully dilated. Among women who had already given birth, that stage lasted just shy of two hours longer.
"We can't fully explain it," said Dr. Katherine Laughon, lead author on the study, who is with the epidemiology branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. "One thing we do know is that epidurals have increased."
Indeed, Laughon and her co-authors posit that changes in obstetric practices could be one of the major factors fueling the change.
More than half of the women in the "modern" cohort had an epidural, versus just 4 percent of the 1960s group. Epidurals have been shown to lengthen labor times -- a 2002 American College of Obstetricians and Gynecologists bulletin said they can prolong labor times by 40 to 90 minutes, while a 2001 study put the average at closer to 25 minutes.
"Clearly, epidurals don't fully explain the 2.6-hour increase," Laughon said.
She also pointed to induction, which she thinks could be another contributing factor. More women today undergo labor induction than in the past.
On average, infants in the contemporary group were also born five days earlier.
"It's surprising, I think, because some people thought that with all of our new controls, and with the use of induction, we'd see shorter times," said Eugene Declercq, a professor in community health services at Boston University. "But that may be counterbalanced by the use of epidurals."
Importantly, moms themselves may also have changed since the 1950s. When comparing the two groups, researchers found that mothers giving birth nowadays had higher body mass index -- a measurement of their weight relative to their height -- and were also several years older. Their babies also tended to weigh more -- all factors that could contribute to longer labor times.
But some experts caution against jumping to conclusions, particularly given limitations in the two data sets.
"The studies compared here have very different patient populations and they are two different study designs," said Dr. Emily DeFranco, an assistant professor in maternal fetal medicine at the University of Cincinnati, who added that the study cannot draw firm conclusions about the possible role of changing obstetrical practices, as it was not designed to look at them specifically.
"I think the way I would interpret it is to say that there are two different studies that have been done that propose what a 'normal' labor curve should look like," DeFranco continued. The current paper suggests that a normal, healthy labor may be slower than previous estimates suggested. Using that looser timeframe, DeFranco said, doctors may be less likely to intervene with a C-section, which are often performed when a woman's labor isn't progressing fast enough.
The authors of the current study agree that further research is required to determine what is driving changes in labor times -- whether it is practice patterns, shifting maternal demographics, or some combination of factors. If that research does support the current findings, Laughon said, it could signal a compelling need to revisit routine interventions.
As for what this means, right now, for expectant mothers?
"This probably all matters a great deal if you're in labor," said Declercq, suggesting that this is data women may want to consider when making decisions about their epidural use, for example. "For me, sitting in my office at my desk, two hours may not seem like much. But for a woman in labor, it is very different."