Contradictory studies have found protective benefits of having children, but this study seems to imply the opposite.

On the whole, data has shown that pregnancy can be protective against aging-related ailments such as cardiovascular disease and cancer.

But a new study suggests that childbearing may speed up cellular aging, although the research stops short of saying pregnancy can be bad for health and longevity.

The study in the journal Human Reproduction concluded that women who bore children experienced advanced cellular aging equivalent to 11 years.

However, that doesn’t mean they will die 11 years earlier than women without children, noted Anna Pollack, PhD, a researcher at George Mason University in Virginia.

Her team examined telomeres, which are parts of DNA that are on the tips of our chromosomes. Some studies have linked shorter telomeres with impaired health and longevity.

This latest study indicates that having more children increases cellular aging — also known as the life history theory (LHT).

This is in contrast with a 2016 study on 75 women that found those who had more children had longer telomeres.

Pollack’s team looked at data on about 2,000 women as part of the National Health and Nutrition Examination Survey.

The study only recorded information on telomere length from 1999 to 2002, so those were the only years used.

“We found that women who had five or more children had even shorter telomeres compared to those who had none, and relatively shorter relative to those who had one, two, three, or four, even,” Pollack said in an interview with Newsweek.

Pollack said that her team didn’t look at whether the type of childbirth — natural vs. cesarean delivery, or C-section — affected telomere length.

Some people might think the study indicates having children makes mothers less healthy, but the authors say those findings should be interpreted with caution.

More research is needed to understand the results — or draw conclusions from them. It’s possible that women who have children started out with shorter telomeres, Pollack noted.

“Women who have had babies do not die younger than those who have not had babies, and they also do not appear to be more susceptible to the common diseases of aging [such as cardiovascular disease, diabetes, cancer, and Alzheimer’s disease],” said Dr. Nanette Santoro, an obstetrics and gynecology professor at the University of Colorado School of Medicine.

“Reproductive fitness seems to correlate with overall physical fitness in most studies,” Santoro added. “My interpretation of these data [is] that we probably don’t know enough about what telomere length is truly telling us to make conclusions at this point in time.”

Longevity is certainly a complex phenotype in that many different factors contribute to the variation in how long people live, added Braxton Mitchell, PhD, a genetic epidemiologist with the University of Maryland School of Medicine.

He noted that a recent study in Nature found that our genes are a factor in our lifespan, but other things are at play.

“If, in fact, having children does shorten telomere length, then perhaps there are other benefits to child-raising — at least in some communities — that offset this,” he said.

Dr. Serena Chen, a reproductive endocrinologist from New Jersey, said she isn’t surprised by the findings.

Carrying a child puts such stress on the body, as it’s one of the hardest things women do.

“Smoking and obesity and just getting older will shorten telomeres,” she noted.

Many women become much less healthy after pregnancy because they never lose the weight they gained while pregnant. That, along with less sleep, could explain some of the factors impacting women’s health.

“Is the actual pregnancy and delivery aging us or is it the lifestyle change that ages us… or is it both?” she asked.

Chen says women can have some control over their health instead of just assuming it may be poorer after having children.

“I would like to think that some of this is partially under our control… that if we take care of our physical and mental health after having a baby, we could have longer telomeres, but that study has yet to be done,” she said.