Overweight mothers run the risk of giving birth to prematurely aged babies susceptible to chronic diseases in later life, research suggests.
A study found a higher body mass index (BMI) before pregnancy was associated with newborns bearing a genetic marker of rapid ageing.
The affected babies had shorter telomeres, which are caps on the ends of chromosomes that protect DNA.
Telomeres shorten each time a cell divides until the cell stops functioning. Short telomeres are a hallmark of advanced biological age, and associated with age-related conditions such as heart disease and type 2 diabetes.
Professor Tim Nawrot, of Hasselt University in Belgium, said: "Compared with newborns of mothers with a normal BMI, newborns of women with obesity are older on a molecular level, because shortened telomere lengths mean that their cells have shorter lifespans.
"So maintaining a healthy BMI during a woman's reproductive age may promote molecular longevity in the offspring."
BMI is a measurement that relates height and weight. An individual with a BMI of 30 or above is considered obese.
Previous studies have shown that adults usually lose about 32.2 to 45.5 molecular units of DNA, or "base pairs", from their telomeres a year.
The new research found that every one point increase in maternal BMI shortened babies' telomeres by 50 base pairs on average. That is equivalent to the amount lost by an adult in 1.1 - 1.6 years of life.
The scientists, who studied 743 mothers and their babies, ruled out other factors associated with telomere length such as parents' age, ethnicity, socio-economic background, smoking habits and birth weight and gender.
The findings are published in the journal BMC Medicine.
