The number of times a woman gives birth may determine how fast she ages

UNIVERSITY PARK, Pa. — Having children and managing a family can certainly make you feel older than you really are. Researchers at Penn State say there’s more truth to this than people may think. Their study finds the number of children women give birth to can determine how fast their body physically ages.

According to their report, the connection between aging and giving birth isn’t a straight line. The Penn State team finds women having either few births or numerous ones actually age faster than mothers giving birth three or four times in life. Researchers add that these changes appear after a woman goes through menopause.

“Our findings suggest that pregnancy and birth may contribute to the changing and dysregulation of several different physiological systems that may affect aging once a person is post-menopause,” says Talia Shirazi, a doctoral candidate in biological anthropology at Penn State, in a media release. “This is consistent with the metabolic, immunological, and endocrinological changes that occur in the body during pregnancy and lactation, as well as the various disease risks that are associated with pregnancy and reproductive investment more generally.”

Study authors say pregnancy and breastfeeding use up a large amount of energy. This can impact several of the body’s functions including the immune system, metabolism, and blood pressure. Women who give birth are also more likely to die from diabetes, high blood pressure, kidney disease, and other illnesses.

“We think there’s something going on, some sort of trade-off, between aging and reproduction,” Shirazi explains. “This makes sense from an evolutionary biology point of view, because if you’re spending energy in pregnancy and breastfeeding, you probably don’t have as much energy to allocate towards things like physiological maintenance and defense.”

‘U-shape relationship between number of births and biological aging’

The study examined 4,418 participants from the Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey. The data included information on whether each person had gone through menopause and how many times they gave birth.

Penn State researchers then measured aging according to nine biomarkers. The biological indicators look at metabolic health, kidney and liver function, blood cell disorders, immune function, and inflammation.

“We wanted to look at measures that would help capture the age and functioning of the body’s major organ systems, instead of looking at aging at the cellular level,” adds Waylon Hastings, a postdoctoral researcher at Penn State. “When we think about pregnancy, we don’t think about changes to individual cells but instead about how the immune system or metabolism changes, for example.”

The results reveal a U-shape relationship between the number of times someone gives birth and biological aging. Women who have between zero and two births or several (more than four) have markers revealing their aging is progressing faster than women giving birth three or four times. The results stay constant even when factoring in lifestyle and demographic difference.

Shirazi believes one possible explanation for this is the presence or lack of ovarian hormones in post-menopausal women.

“Previous research has found that generally, ovarian hormones are protective against some cellular level processes that might accelerate aging,” Shirazi explains. “So it’s possible that in pre-menopausal women the effect of hormones are buffering the potential negative effect of pregnancy and reproduction on biological age acceleration. And then perhaps when the hormones are gone, the effects can show themselves.”

The study appears in the journal Scientific Reports.