"For single [birth] defects, the risk is three to four times greater, and about eightfold for multiple defects," says Adolfo Correa, MD, MPH, PhD, the study's lead author and an epidemiologist at the CDC's National Center on Birth Defects and Developmental Disabilities.
While the diabetes-birth defects link has been long known, this new research breaks new ground, says Correa.
"This is the largest study of its kind done on diabetes and birth defects," he tells WebMD. The scope was broader than other studies, too, since the researchers looked at those with diabetes as well as gestational diabetes. And they looked at nearly 40 defects, both cardiac and noncardiac.
Even so, another expert cautions that women, even those with diabetes and planning a pregnancy, should not become frightened by the latest research. Ninety-three percent of the birth defects weren't associated with maternal diabetes. Two percent of the children with single birth defects were born to mothers who had diabetes before their pregnancy, while 5% of those born with multiple defects were born to diabetic moms.
Diabetes and Birth Defects
Correa and his colleagues evaluated mothers of more than 13,000 infants with birth defects and nearly 5,000 infants without birth defects. The children were born between 1997 and 2003 and were participants in the National Birth Defects Prevention Study, which drew data from 10 birth-defect surveillance systems in 10 states.
They looked at whether a mother had diabetes, either type 1 or type 2, before becoming pregnant or whether she developed it during pregnancy. Women also reported other information, including height and weight, so their BMI could be calculated. Twenty-four mothers of the nearly 5,000 infants without birth defects had diabetes before pregnancy; 283 moms of the babies with birth defects had diabetes before pregnancy.