Regular moderate-intensity aerobic exercise during pregnancy may lead to a modest reduction in infant birth weight. Birth weight is an important indicator of infant health. Talk to your health care provider to determine a level of exercise that is appropriate for you.
Research
Regular exercise among pregnant women may lead to lower birth weight, according to a 2010 study in "The Journal of Clinical Endocrinology & Metabolism." In the study, a group of healthy, pregnant women participated in a cycling program from 20 weeks pregnant to delivery. Compared with a control group, those who exercised had babies that weighed an average of 5 oz. less, although both sets of babies had healthy weights. The researchers suggested that exercise results in lower birth weight because it regulates nutrient supply to the fetus.
Significance
Infant birth weight is important because larger birth size is associated with higher risk for childhood obesity. Newborn babies on the lower end of the normal weight range are generally healthier, according to "Time." Babies weighing more than 8 lbs., 12 oz. are more likely to be overweight in childhood and adolescence, according to an article in the "Journal of Family Practice." Overweight children are at risk for other health problems, including depression, asthma, insulin resistance and hypertension.
Insulin Resistance
Some researchers didn't expect exercise to lead to lower birth weights because exercise tends to lower the risk of insulin resistance. Insulin resistance, a precursor condition to diabetes that often occurs during pregnancy, can actually be helpful to fetal development. In pregnant women, the placenta produces hormones that disrupt insulin's role in the body, delivering nutrients to the fetus. But in the 2010 study, both the exercisers and the control group developed insulin resistance, leading researcher Dr. Paul Hofman to suggest that the development of insulin resistance in pregnant women is a survival mechanism that ensures the fetus receives enough food.
Recommendations
Start slowly if you are a pregnant woman who is new to exercising. If you've been exercising regularly prior to pregnancy, you should be able to keep up your program with some modifications for much of your pregnancy. Reduce your intensity or work out for shorter periods if you feel fatigued. Don't exercise until you are breathless or your baby will not receive enough oxygen. Avoid contact sports, exercising in hot weather and unstable terrain. Drink plenty of fluids before, during and after exercise.
