Obese pregnant women can avoid weight gain or even lose some weight without harming their babies, a small study suggests.

In fact, researchers found, obese women who maintained their weight or shed pounds during pregnancy were more likely to have a normal-weight newborn than those who gained pregnancy pounds.

The notion that it’s all right for obese women to avoid weight gain during pregnancy is fairly controversial, said Dr. Raul Artal, an obstetrician at St. Louis University and the lead author of the new study.

In the U.S., he told Reuters Health, most obstetricians follow guidelines devised in 1990 that recommend obese women gain about 13 pounds during pregnancy. That’s far less than the 25 to 35 pounds recommended for normal-weight women, but still a substantial amount of weight for women who are already heavy.

Those guidelines deserve a second look, Artal argued. For obese women, he said, weight maintenance or even modest weight loss may not only do no harm to mother and child, but might benefit them.

For their study, Artal and his colleagues followed 96 obese pregnant with gestational diabetes - a form of diabetes that emerges during pregnancy.

Fifty-seven of the women enrolled in a diet program, while the rest began a diet-and-exercise program. Both groups received help devising a healthy, lower-calorie eating plan, while women in the exercise group had supervised, moderate workouts, such as treadmill walking, once a week. Exercisers were also encouraged to walk or perform other low-impact activities on their own every day.

In the end, Artal’s team found, women who dieted and exercised gained less weight than women who only changed their eating habits.

Moreover, women who shed pounds or maintained their weight - regardless of the group they were in - were less likely to have a larger-than-normal newborn. There was no evidence that weight loss increased the risk of pregnancy complications or harmed fetal growth, the researchers report in the journal Applied Physiology, Nutrition, and Metabolism.

Because it’s so difficult for obese women to shed pounds gained during pregnancy, Artal said, preventing the weight gain could bring longer-term health benefits.

“Pregnancy is not a state of confinement,” he said, and overweight women should not be afraid of moderate physical activity. “All we’re talking about is a brief walk after each meal,” Artal noted.

That said, he advised that pregnant women still talk to their doctors before taking up an exercise routine, to make sure they have no conditions that preclude physical activity. Women should also get advice from a nutritionist on how to make healthy diet changes.

SOURCE: Applied Physiology, Nutrition, and Metabolism, June 2007.