SAN DIEGO – Women who develop diabetes during pregnancy give birth to healthier babies if they are aggressively treated, concludes a large new study that helps bolster the case for testing all pregnant women for this condition.

The study, by Australian researchers, is the first to show that treatment can help avoid serious problems at birth.

Although complications are uncommon, they were four times lower among babies of mothers who were aggressively treated. No babies born to the 490 women getting more aggressive care died. There were three stillbirths and two other infant deaths among the 510 mothers who got regular care.

Results of the study will be published in the New England Journal of Medicine on Thursday and were presented Sunday at an American Diabetes Association meeting.

Gestational diabetes sometimes begins or is diagnosed in mid-pregnancy and disappears later. Women who get it have a greater chance of having diabetes in the future. Doctors don’t know if there’s a risk to babies.

It affects 3 percent to 7 percent of pregnant women in the United States, a number that is on the rise because of the growing obesity problem.

Doctors have long wrangled over whether babies would benefit if expectant mothers were tested and treated for the problem, and previous studies have had conflicting conclusions.

The American College of Obstetricians and Gynecologists backs diabetes screening for all pregnant women. The U.S. Preventive Services Task Force, a federal panel that makes recommendations on health issues, has not taken a stand, citing weak evidence.

In the study, researchers followed 1,000 women with gestational diabetes. During their third trimester, the women were separated into two groups: One group aggressively managed their diabetes through special diet, blood sugar monitoring and insulin therapy. The other had typical prenatal care.

Four percent of babies whose mothers received routine care developed complications – such as shoulder damage, bone fracture, nerve problems or death – compared to 1 percent of babies whose mothers had aggressive care.

Women who tightly controlled their diabetes were less likely to deliver extremely large babies weighing more than 8 pounds – 21 percent of babies whose mothers were regularly treated were oversized compared to 10 percent in the other group.

Researchers compared depression and mood in 573 mothers three months after delivery and found women who were rigorously treated fared better.

Another study presented at the meeting found that Type 1 diabetics who closely watched their blood sugar levels dramatically cut their risk of heart disease even if they relaxed their control later on. Type 1 diabetics make up 5 percent to 10 percent of the 18 million Americans who have the disease.

Heart disease is the leading cause of diabetes-related deaths, and diabetics are more than twice as likely to die from it than non-diabetics.