Babies whose mothers are obese may be biologically "older" than babies whose mothers are a normal weight, a new study from Belgium suggests.

Researchers analyzed information from 743 mothers ages 17 to 44, and their newborn babies, using samples of umbilical cord blood obtained from each newborn immediately after delivery.

The researchers looked at the genetic material inside the babies' cells, specifically the length of their telomeres, which are the caps on the ends of chromosomes that protect the chromosomes from damage. Telomeres naturally shorten as people age, but they don't shorten at the same rate in every person. The longer a person's telomeres, the more times their cells can still divide. Thus, telomeres are considered a marker of biological age — that is, the age of a person's cells, rather than their chronological age.

The researchers found that, compared to newborns whose mothers were a normal weight, the newborns whose mothers were obese had shorter telomeres. [7 Ways Pregnant Women Affect Babies]

A 1-point increase in the mother's body mass index (BMI) was linked with a shortening of telomeres in the newborns by about 50 base pairs. (If you think of a DNA molecule as a ladder, the base pairs would be the "rungs" of the ladder.) This 50-base-pair shortening is equivalent to the length of a telomere that an adult would typically lose in a little over one year, the researchers said.

"Our results add to the growing body of evidence that high maternal BMI impacts fetal [DNA] programming, which could lead to altered fetal development and later life diseases," study co-author Tim Nawrot, a professor of environmental epidemiology at Hasselt University in Belgium, said in a statement. In adults, shorter telomeres are linked with age-related diseases, such as heart disease and type 2 diabetes.

The findings held even after the researchers took into account other factors that may impact telomere length in newborns, including the parents' age, socioeconomic status and smoking habits, and the baby's birth weight.

Still, the study only found an association, and the findings cannot prove that a mother's weight can cause a shorter telomere length in a baby. The researchers noted that they did not have information about the weight of the father, which might also influence the babies' telomeres.

The study was published today (Oct. 17) in the journal BMC Medicine.

Original article on Live Science.

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