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Exercise During Pregnancy for Smaller Baby

Moderate Exercise During Pregnancy Lowers Baby's Birth Weight, May Reduce Baby's Risk of Obesity

Exercise During Pregnancy: Results continued...

Researchers initially believed the exercising mothers would become less insulin-resistant.  Typically, Baldi says, a woman becomes more insulin-resistant during pregnancy, a normal occurrence within certain boundaries. "It has a lot to do with hormonal changes," he says. If a woman becomes too insulin-resistant, gestational diabetes can occur.

"It did not come out as we suspected," Baldi tells WebMD, with no substantial differences found in insulin resistance between the two groups.

The difference, says Baldi and Hofman, may be because of other factors, such as differences found in certain growth factors. Another possible explanation, Hofman says, is slightly reduced blood flow that occurs to the placenta during exercise and for several hours afterward.

Exercise During Pregnancy: Other Input

The finding of lower birth weights of infants of exercising mothers is not surprising to Linda May, PhD, an associate professor of anatomy at the Kansas City University of Medicine and Biosciences in Kansas City, Mo., who has also researched the topic.

The finding that there was no change in insulin sensitivity between groups was surprising, she tells WebMD.

Her research has found that during pregnancy, more exercise [within recommended amounts for an individual] yields more benefits.

More study is needed on high-risk pregnant women, Hofman and May say. The women in the study, exercisers and non-exercisers, were not high risk.

For most healthy pregnant women, Hofman says, the research seems to support exercising at least 30 minutes a day moderately, and probably more. Some studies, he says, have demonstrated up to 60 minutes daily is generally safe.

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