Pregnant women who have above-normal blood sugar levels are twice as likely to have overweight children, says the largest study to confirm a link between maternal blood sugar and the risk of future obesity in offspring.

The research, which included Hawai'i mothers and their children, found that women whose sugar levels were higher than normal, but not high enough to be classified as diabetes, were more likely to have obese children than either those with normal blood sugar or those with diabetes who were treated to reduce their blood sugar levels.

"The good news about this study is it appears the risk of obesity is potentially reversible" by treating high blood sugar levels during pregnancy, says endocrinologist Teresa Hillier, a co-author of the study. She and colleagues at Kaiser Permanente's Center for Health Research looked at 9,439 mother-child pairs enrolled in Kaiser Permanente's Hawai'i and Northwest regions between 1995 and 2000. The study was published in the September issue of the journal Diabetes Care

The researchers found that the higher the mother's blood sugar level during pregnancy, the greater the chance that the child would be obese by the age of 5 to 7 years. The finding was true for all racial and ethnic groups.

Women with pre-existing diabetes were not included in the study, which was designed to learn how gestational diabetes — the form that appears for the first time during pregnancy and often disappears after the baby is born — affects a child's risk for future obesity.

During pregnancy, hormones are produced that increase the need for insulin. If the mother's pancreas can't make enough extra insulin, her blood sugar level rises. It may normalize after delivery, but women who have gestational diabetes face an increased risk of developing diabetes later in life.

Previous studies have found an association between childhood obesity and gestational diabetes in special populations, such as Pima Indians, but this is the largest study to make that link in a diverse population, and the first to suggest the risk is reversible, Hillier says.

Pregnant women are routinely screened for diabetes at 24 to 26 weeks of pregnancy, or earlier if there are risk factors such as obesity or family history of diabetes. Those found to have blood sugar high enough to be diagnosed with diabetes are treated with diet, exercise and sometimes insulin.

The study "says to women, A, you need to know what your blood sugar is, and B, it needs to be normal to protect your baby," says endocrinologist Larry Deeb, president of the American Diabetes Association.

The findings show that any elevated blood sugar during pregnancy is of concern and should be treated with diet, exercise and possibly insulin, he says.