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 received aggressive care.

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 to be presented Sunday at an American Diabetes Association meeting in San Diego.

Growing Obesity Problem

Gestational diabetes 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 gestational diabetes. Previous studies on this topic have led to conflicting conclusions.

An influential doctor group, the American College of Obstetricians and Gynecologists, backs diabetes screening for all pregnant women. The US Preventive Services Task Force, a federal panel that makes recommendations on health issues, has not taken a stand, saying evidence is lacking to rule one way or the other.

Dr. Diana Petitti, vice chair of the task force, declined to comment specifically on the Australian study, but said the group always considers the latest research in deciding whether to update guidelines.

Better Birth Outcomes

In an accompanying editorial, Dr. Michael Greene, an obstetrician at Massachusetts General Hospital who had no role in the study, wrote that the latest study "provides some long-awaited evidence to support the use of screening and treatment for women at risk."

Gestational diabetes sometimes begins or is diagnosed in mid-pregnancy and disappears later. Women who get it have a greater chance of developing diabetes in the future. However, doctors do not know if there's a risk to babies.

In the study, researchers followed 1,000 women diagnosed with gestational diabetes. During their third trimester, the women were separated into two groups: One group was taught to aggressively manage their diabetes through special diet, blood sugar monitoring and insulin therapy. The other group received regular prenatal care.

Researchers found that aggressive treatment was linked to better birth outcomes. 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 received 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 also compared depression and mood in 573 mothers three months after delivery and found that women who were rigorously treated fared better.