Having Children Makes Women's DNA Look 11 Years Older Than It Should

pregnancy telomeres
A doctor examines a woman who is eight months pregnant at Inner City Health Center in Denver, Colorado, on March 15, 2017. JASON CONNOLLY/AFP/Getty Images

As any mother will tell you, having kids does a lot to a person's body—and new research suggests it may even change a woman on a cellular level. Sections of genetic material associated with lifespan called telomeres are shorter in women who have given birth, according to a paper published February 14 in Human Reproduction. Specifically, the telomeres of women who have had children are as short as if they were childless and 11 years older.

Telomeres, discovered in the 1970s, are strings of DNA molecules at the ends of all our chromosomes that act a little like the plastic bits on the ends of shoelaces. Because of the way DNA is replicated as our cells replicate and divide and age, these caps get worn down over time. However, wearing down these caps is better than the alternative—which would be wearing down the important genetic material of the chromosome itself. If the telomeres are completely gone, the cell wouldn't be able to replicate at all, George Mason University researcher Anna Pollack told Newsweek.

For the record, it's not that women who have had kids are dying 11 years earlier than their childless peers—nor does Pollack think that the study should be seen as a sign that women should stop having children, either. Lots of things can affect a person's telomeres, including smoking, being overweight and stress. In general, people in this study lost about 10 base pairs of DNA each year. But women who had a child had 116 base pairs fewer than women their age who hadn't had a child.

"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.

The data for this study were actually collected nearly 20 years ago as part of the federal government's regular National Health and Nutrition Examination Survey. For the 1999-2002 survey, thousands of people had their telomere lengths analyzed by one of the people who first discovered them: Elizabeth Blackburn. (Blackburn and two others shared the Nobel Prize in 2009 for their work on telomeres.) But the survey just recently released the telomere data set to the public, Pollack noted. That data set included information from the nearly 2,000 women who were included in this study.

Pollack and her team's findings fit in with other research that's been done—and with people's personal experience. "Anecdotally, just chatting with my friends who have children, we all do feel that having kids has aged us," Pollack said. "But scientifically, this does fit with what we understand pretty well. We know that having kids is associated with a higher risk of heart disease and diabetes. And some large studies have linked telomere length to mortality risk and risks of other major diseases."