Expectant mothers who perform regular moderate-intensity exercise reduce their baby’s birth weight, possibly lowering the child’s obesity risk in the future, according to a study published in the Journal of Clinical Endocrinology & Metabolism.

For the study, researchers randomly assigned 84 first-time pregnant women to an exercise or control group. The exercise group participated in five, 40-minute stationary cycling sessions weekly. (Moms-to-be cycled for at least 36 weeks into their pregnancies.)

Researchers found babies born to the exercise group were 143 grams (0.3 lbs) lighter and had a lower body mass index (height to weight ratio) compared with those born to mothers in the control group.

Study findings showed that regular aerobic exercise affected the baby’s maternal environment and triggered nutrient stimulation of fetal growth and reduced birth weight, said study coauthor Paul Hofman, MD, of the University of Auckland in New Zealand.

“Given that large birth size is associated with an increased risk of obesity, a modest reduction in birth weight may have long-term health benefits for offspring by lowering this risk in later life,” Hofman added.

The findings also suggest that regular training during pregnancy will not have a major adverse effect on insulin resistance, Hofman said.

Read RH’s “ Fit Mamas” for tips on safely staying in shape during pregnancy.