Experiments on pregnant mice that voluntarily exercised found their offspring were more physically active.
Professor Robert Waterland said although the study involved lab rodents “several human studies have reported results consistent with ours.”
For example, observational studies have found women who work out when they are pregnant have children who tend to be fitter.
But these results could be attributed to the mothers’ influence on the children after they were born. Or, mothers could pass to their offspring a genetic predisposition to be physically active.
Prof Waterland, of Baylor College of Medicine, Houston, said: “Our study in a mouse model is important because we can take all those effects out of the equation.
“We studied genetically identical mice and carefully controlled the amount of physical activity of the mothers before pregnancy.”
For the study published in The FASEB Journal, female mice that enjoyed running were selected and then divided into two groups, with one allowed access to running wheels before and during pregnancy, while the other was not.
During early pregnancy, the females with running wheels ran an average of 10 kilometres (6.2 miles) a night. They ran less as pregnancy progressed, but even by the beginning of the third trimester they ran, or walked, about 3 kilometres (1.9 miles) nightly.
The researchers found the mice born to mothers that exercised were about 50 per cent more physically active than those whose mothers did not.
Importantly, their increased activity persisted into later adulthood, and even improved their ability to lose fat during a three week voluntary exercise program.
The study supports the idea movement during pregnancy influences a baby’s brain development in the womb, making it more physically active throughout life.
Prof Waterland said: “Although most people assume an individual’s tendency to be physical active is determined by genetics, our results clearly show the environment can play an important role during foetal development.”
If a similar effect can be confirmed in people, it could represent an effective strategy to counteract the current worldwide epidemic of physical inactivity and obesity.
Increasing physical activity has major health implications. According to the World Health Organization, insufficient physical activity is one of the ten leading risk factors for death worldwide.
Several expert groups including the American College of Obstetricians and Gynaecologists already recommend, in the absence of complications, pregnant women get 30 minutes or more of moderate exercise a day.
Added Prof Waterland: “I think our results offer a very positive message. If expectant mothers know exercise is not only good for them but also may offer lifelong benefits for their babies, I think they will be more motivated to get moving.”
Previous research has shown exercising in pregnancy also helps babies develop healthy hearts. Scientists believe it programmes a baby’s arteries to resist heart problems.
At present, women are advised that the more active and fit they are during pregnancy, the easier it will be to cope with labour and get back into shape after the baby arrives.