Aerobic exercise during pregnancy reduces birth weight of baby

April 5, 2010 by Shawn Douglas
Filed under: News, Pregnancy

Regular aerobic exercise during pregnancy is likely to reduce a baby’s birth weight and reduce the risk of obesity later in childhood.

A growing body of evidence suggests that regular moderate exercise during pregnancy is healthy for both mother and child. A joint study out of the U.S. and New Zealand on 84 first-time mothers has recently added to that evidence.

The team of researchers, based out of the University of Auckland in New Zealand and Northern Arizona University in the United States, divided the 84 mothers into two groups: one group who exercised regularly and one control group. The women in the exercise group were instructed to perform 40 minutes of exercise on an exercise bike no more than five times a week. The routine had to continue until at least the thirty-sixth week of gestation.

Researchers also gauged insulin sensitivity in the women during the pregnancy. Insulin is an important hormone which helps regulate the flow of nutrients to the baby during pregnancy. There have been previous concerns about a woman’s maternal insulin sensitivity while exercising, with fears that too much exercise adversely restricts fetal nutrition.

After measuring birth weights and body mass indexes (BMI) of the babies within 48 hours of birth, the teams analyzed their data, finding that the babies of the women from the exercise group were approximately 0.32 pounds (143 grams) lighter than those of the women in the control group. More importantly, the teams found that insulin sensitivity in the mothers didn’t seem to disrupt fetal nutrient flow.

“The physiological response to pregnancy appears to supersede the chronic improvements in insulin sensitivity previously described in response to exercise training in non-pregnant individuals,” said Dr. Paul Hofman of the University of Auckland, co-author of the study.

“Our findings show that regular aerobic exercise alters the maternal environment in some way that has an impact on nutrient stimulation of fetal growth, resulting in a reduction in offspring birth weight,” added Hofman. “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.”

In the U.K., official medical guidance already encourages women to take light exercise regularly and not to overeat during pregnancy.

The team will have their study results published in the May issue of the Journal of Clinical Endocrinology & Metabolism.