If you're having a healthy pregnancy, stay active and work with your doctor and a certified exercise professional to develop an exercise plan.

Even if you haven't been exercising, you can start an exercise program while pregnant.

RODALE NEWS, EMMAUS, PA—Many studies have found that what goes on while a baby is growing in a mother's belly can affect the health of the child long after he or she has left the womb. And new evidence gives yet another reason for expecting mothers to get active. Women who exercise regularly during pregnancy are more likely to give birth to babies with a lower, but healthier, birth weight, according to a study that will appear in the May issue of the Journal of Clinical Endocrinology & Metabolism. That could set up the child for a healthier life, since a too-high birth weight is an indicator of childhood obesity, a growing national problem.

THE DETAILS: In the small study led by New Zealand researchers, about half of the 84 women (average age 30) performed an exercise routine throughout the second half of pregnancy, while the other women did not. The exercising woman participated in at-home, stationary-cycling exercises starting 20 weeks into their pregnancy and continuing throughout. Women were prescribed a maximum of five moderate intensity, 40-minute cycling sessions per week. Mothers in the exercising group gave birth, on average, to babies five ounces lighter than the non-exercising mothers.

WHAT IT MEANS: As long as your obstetrician gives you the green light, moderate aerobic exercise during pregnancy is a great way to boost the health of mother and child. Researchers already know that exercising during a normal pregnancy can help prevent gestational diabetes and improve the endurance fitness of a mother, which can lead to a speedier, less complicated delivery. The more recent findings pointing to a mother's exercise leading to a more normalized birth weight show that exercising throughout pregnancy can have lasting health benefits for a child, since larger babies are more prone to childhood obesity.