A new target of 90 may be more reasonable, Metzger said. Researchers are not making recommendations for now, he said. New guidelines may come next year after international experts meet to analyze the findings, he said.

In the study, large babies were born 5 percent of the time to women with the lowest level of fasting blood sugar (less than 75 milligrams per deciliter). The rate of large babies was 27 percent at the highest level (greater than 100 milligrams per deciliter).

Other measures of gestational diabetes in the pregnant women, such as glucose tolerance tests, also correlated with infant risk.

The risk was seen in babies in the United States, Canada, Barbados, Britain, Israel, Thailand, Australia, Singapore and Hong Kong. The $19 million study was funded by the National Institutes of Health and the diabetes association.

Gestational diabetes affects about 4 percent of pregnant women, about 135,000 a year in the United States. That number may climb by tens of thousands of women a year if guidelines are revised, Metzger said.

"The question is, what is the best blood sugar to have? Probably there is no threshold. The lower, the better," said Dr. Joel Zonszein, director of the Clinical Diabetes Center at New York's Montefiore Medical Center.

Dr. John Kitzmiller, a maternal and fetal health expert at Santa Clara Valley Medical Center in San Jose, Calif., said the study will raise debate over how to treat women with mild elevations in blood sugar. More evidence may be needed to show that treatment works.

Women with gestational diabetes are treated with special diets that limit carbohydrates and include high-fiber foods in frequent smaller meals. They sometimes also require injected insulin at a cost of $80 to $120 a month and need regular doctor checkups.

Some doctors use glyburide, a generic glucose-lowering pill, but large studies of the drug's safety in pregnant women have not been done.

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