Gestational diabetes can cause the fetus to grow too large. (Javier Galeano/AP Photo)

Treating mild diabetes that develops during pregnancy helps prevent serious problems that can occur when an infant gains too much weight, a new U.S. study suggests.

Women with gestational diabetes — temporarily high blood sugar levels during pregnancy — have a higher risk of cardiovascular disease than the general population.

The condition can also cause the fetus to grow too large and require delivery by caesarean section. Such children are at greater risk of becoming obese when young and developing Type 2 diabetes as adults.

About four per cent of pregnant women in the United States develop gestational diabetes, resulting in about 135,000 cases a year, said Dr. John Thorp, the study's author and a professor of obstetrics and gynecology at the University of North Carolina at Chapel Hill.

In a study of 958 women that appears in Thursday's issue of the New England Journal of Medicine, researchers found that, compared to women with untreated diabetes, those treated for mild gestational diabetes had:

· Fewer babies that were overly large (7.1 per cent versus 14.5 per cent). · Fewer cesarean sections (26.9 per cent versus 33.8 per cent). · Less shoulder damage during birth (1.5 per cent versus 4.0 per cent).

"There is every reason to fully treat women with even the mildest [gestational diabetes] based on our results," said the study's leader, Dr. Mark Landon of Ohio State University Medical Center in Columbus.

The study started with women who were between 24 and 31 weeks pregnant. They were randomly assigned, with 485 women receiving treatment, including dietary changes, blood-glucose monitoring and insulin, if necessary, and 473 getting no treatment.

There were no deaths in either group, and no difference in other birth-related complications.

Excess weight gain minimized

Of those in the treatment group, 93 per cent were able to keep their blood sugar under control through diet alone. The other seven per cent needed insulin.

Eating a healthier diet could even help other pregnant women avoid excess weight gain, said Dr. David Sacks of Kaiser Foundation Hospital in Bellflower, Calif., who wrote a journal commentary accompanying the study.

"Although further research is needed, a focus on monitoring and minimizing excessive weight gain during pregnancy for all women seems to be a prudent and inexpensive policy, the benefits of which, for both mother and baby, may extend far beyond birth," Sacks wrote.

Diet change 'hard work'

But modifying a diet during pregnancy isn't easy, said Lorenda Donaugh, who was diagnosed with a mild case of gestational diabetes at 28 weeks.

"I knew it was going to be hard work," the 27-year-old said of meal planning and cutting back on sugar. "It takes a lot of time and planning."

Donaugh was not part of the study but works with Landon doing ultrasounds. Besides changing her diet, she monitored her blood sugar, took extra walks and eventually took a diabetes medication. Both mom and daughter gained healthy amounts of weight.

Risk factors for gestational diabetes include being over age 25, being obese and having a family history of diabetes.

With files from The Associated Press