Diabetic women who get pregnant are three to four times more likely to have a child with birth defects than other women, according to new U.S. government research.
The study is the largest of its kind, and provides the most detailed information to date on types of birth defects that befall the infants of diabetic mothers, including heart defects, missing kidneys and spine deformities.
The study lists nearly 40 types of birth defects found to be significantly more common in the infants of diabetic mothers than in those who weren't diabetic or who were diagnosed with diabetes after they became pregnant.
The study's list of diabetes-associated birth defects is surprising. It's much longer than was previously understood, said Janis Biermann, senior vice-president for education and health promotion at the March of Dimes.
"It adds more information about the specific types of birth defects associated with pregestational diabetes and gestational diabetes," said Biermann, who was not involved in the research.
Researchers from the U.S. Centers for Disease Control and Prevention led the study, which is being published in the American Journal of Obstetrics and Gynecology. CDC officials released the study Wednesday.
Birth defects affect one in 33 babies born in the United States, and cause about one in five infant deaths. The cause of most birth defects isn't known but some risk factors include obesity, alcohol, smoking and infections.
Excess sugar harms infants
Doctors have known for decades about the threat diabetes poses to pregnancies. Past research has focused on dangers to the infant by the extra amounts of glucose — sugar — circulating in the womb of a diabetic mother. Studies with rats and mice clearly show excess sugar harms fetal tissue development, said Dr. E. Albert Reece, a study co-author, who directs birth defects research at the University of Maryland School of Medicine.
The new study draws from the birth records between 1997 and 2003 at hospitals in 10 states: Arkansas, California, Georgia, Iowa, Massachusetts, New Jersey, New York, North Carolina, Texas and Utah.
The study focused on the 13,000 births involving a major birth defect, and compared them to nearly 5,000 randomly selected healthy births from the same locations.
Mothers were asked if they had been diagnosed with diabetes before or during their pregnancy. The researchers said those who were diagnosed while pregnant either had a temporary, pregnancy-induced condition called gestational diabetes or had diabetes that had gone undiagnosed until they were pregnant.
The study found that there was no diabetes involved in 93 per cent of the birth defects.
About two per cent of the children with single birth defects were born to mothers who had diabetes before they became pregnant. About five per cent of the infants with multiple defects were born to mothers with that condition. In healthy births, the percentage of mothers who were diabetic before pregnancy was much lower.
The study also showed a wide range of birth defects that included malformation of the heart, spine, limbs and gastrointestinal tract.
"Diabetes is not discriminating" in the birth defects it's linked to, said Dr. Adolfo Correa, a CDC epidemiologist who was the study's lead author.