Fit Pregnancy, Fit Babies
Reported April 09, 2010
(Ivanhoe Newswire) — Pregnant women who engage in regular moderate-intensity aerobic exercise will have babies whose birth weight is slightly lower without restricting the development of maternal insulin resistance, which is essential in maintaining nutrient availability to the fetus.
Increased size at birth is associated with greater risk for the development of childhood obesity. This study is the first to demonstrate a significant effect of non-weight bearing exercise, such as stationary cycling, on birth weight.
“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,” co-author Paul Hofman, M.D., of the University of Auckland in New Zealand, was quoted as saying. “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.”
This study also evaluated changes in insulin sensitivity in response to aerobic exercise during pregnancy. Maternal insulin resistance has been correlated with birth size. Exercise has been shown to reduce insulin resistance, but findings from this study suggest that regular exercise during pregnancy does not cause the same reduction in insulin resistance that occurs in exercising non-pregnant individuals.
“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,” Dr. Hofman said. “This may be an important finding for athletes who want to continue regular training during their pregnancy, as it suggests that training will not have a major adverse impact on insulin resistance.”
In this trial, researchers assigned 84 first-time mothers to either exercise or control groups. Participants in the exercise group utilized stationary cycling and were individually prescribed a maximum of five 40-minute sessions of aerobic exercise per week. The exercise group was instructed to maintain the exercise program until at least 36 weeks gestation. Insulin sensitivity was assessed at 19 and 34 to 36 weeks gestation using an intravenous glucose tolerance test. Birth weight and BMI at birth were measured within 48 hours of birth.
Exercise training had no effect on maternal body weight or BMI during late pregnancy. Furthermore, exercise had no effect on insulin resistance from baseline to late gestation, and did not affect any other parameters of glucose regulation. Offspring of exercisers were on average lighter than their control counterparts, although there was no difference in birth length. Exercise training also resulted in lower BMI for the babies.
SOURCE: Journal of Clinical Endocrinology & Metabolism (JCEM), April 5, 2010