New research suggests that the number of times a person gives birth may affect the body’s physical aging process, according to study results published in Scientific Reports.

Investigators examined several different measures that represent how the body ages and noted that pregnancy and breastfeeding use a large amount of energy and can affect many systems, including immune function, metabolism, and blood pressure. Additionally, individuals who have given birth are more likely to die from diabetes, kidney disease, hypertension, and other conditions than those who have not given birth, according to a press release.

“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,” said study author Talia Shirazi, a PhD candidate at Penn State, in a press 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.”

Investigators used data on 4418 participants from the CDC’s National Health and Nutrition Examination Survey, including information about reproductive health, the number of live births, and whether individuals had gone through menopause or not. The team measured biological aging in several ways based on 9 biomarkers designed to assess metabolic health, kidney and liver function, anemia and red blood cell disorders, and 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,” said study author Waylon Hastings, PhD, in the press release. “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.”

According to the study results, the investigators found a U-shaped relationship between the number of live births and accelerated biological aging. Individuals who reported zero or fewer live births and those who reported many live births had markers of quicker aging than those who reported 3 or 4 births. The investigators found that this was true even when controlling for chronological age, lifestyle, and other health-related and demographic factors.

Although it is not currently possible to know what caused these associations, Shirazi said a possible explanation may be 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 said in the press release. “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 investigators also said their findings suggest that additional research can be done to understand the processes that may be involved in the connection between aging and having children, as well as how these processes work over time.

The number of times a person gives birth may affect how quickly they age [news release]. EurekAlert; November 30, 2020. Accessed December 7, 2020.