Telomeres are the end sections of chromosomes that help DNA replication and shorten over time because DNA polymerase is unable to synthesize a copy of DNA from the end. Telomere length is often associated with a person’s lifespan and predisposition to disease. A study conducted by researchers at George Mason University found that the telomeres of women who have given birth are shorter than those of women who do not have children.

The scientists chose a simple way to check. They used statistics from the National Health and Nutrition Examination Survey, a program run by the U.S. Department of Health and Human Services. A total of 1,954 questionnaires were used in the study of women who were screened between 1999 and 2002, because that was the time period when physicians measured patients’ telomere length.

The comparison showed that women who gave birth had shorter telomeres compared to the control group, a difference estimated by scientists at 11 years. This figure is even higher than in studies related to smoking and obesity. Dr. Anne Pollack, who led the work, commented on the observation:

“So far, we can’t say unequivocally that shortened telomeres are related to childbirth. Perhaps they were shorter initially, or perhaps stress or other factors contributed to the decrease in length. More research will be needed to determine the causes.”

The authors of the paper also note that they did not obtain data on women’s reproductive status, stress levels or other factors during the study. Telomere size is not always associated with positive trends, with some scientists suggesting that long telomeres contribute to cancer.