WASHINGTON - A change in testing could nearly triple the number of women diagnosed with diabetes during pregnancy, but would catching milder cases help mother or baby? A government panel is urging more research to find out.

Gestational diabetes is a growing problem. More women are getting it as they wait until their 30s or later to have a baby, and as they increasingly begin their pregnancies already overweight.

This is one of the most common complications of pregnancy, and just about every woman gets checked for it. That's because if mom's high blood sugar isn't controlled, the fetus can grow too large, leading to C-sections and early deliveries.

There are other problems: Mom can get high blood pressure; the baby can be born with low blood sugar; the baby's risk of obesity in childhood is increased.

Doctors today diagnose gestational diabetes in about 5 percent to 6 percent of U.S. pregnancies, or about 240,000 a year, according to experts convened this week by the National Institutes of Health.

Most U.S. doctors use a two-step testing method. But now there's a push for doctors to switch to a simpler one-step test backed by the American Diabetes Association and World Health Organization. It lowers the blood sugar threshold for diagnosing the condition.

On Wednesday, the NIH-appointed panel said up to 20 percent more pregnant women would be classified with gestational diabetes if that test were adopted.

The more aggressive approach treats milder cases with diet and exercise, not medication. But that's still a lot of women who would get extra medical care.

There's been no study of whether treating milder cases makes any difference to the health of mother and baby, the experts concluded.