Pre-existing maternal diabetes still major risk factor for congenital heart defects

By Eleanor McDermid

The strong influence of pre-pregnancy diabetes on the likelihood of women giving birth to babies with congenital heart defects (CHDs) has not lessened over recent decades, say researchers.

The study of more than 2 million babies born in Denmark between 1978 and 2011 showed that the prevalence of CHDs was fourfold higher among babies born to women with pre-existing diabetes relative to those without, at 318 versus 80 per 10,000 births.

In all, 0.36% of babies were born to mothers with pre-existing diabetes, and 39.3% of these mothers had a record of acute diabetes complications (eg, coma, ketoacidosis) prior to their pregnancy. This pushed the risk of CHDs in their babies even higher, at 6.06- and 7.38-fold for one complication and two or more acute complications, respectively.

This finding suggests "a role for glucose in the causal pathway", say Nina Øyen (Statens Serum Institut, Copenhagen, Denmark) and study co-authors in Circulation.

The team found that the increased risk associated with maternal diabetes was similar for most types of CHD, "suggesting that maternal diabetes impacts general cardiac development very early in embryogenesis."

In the earliest period of the study, 1978-86, 79% of CHD cases among babies of diabetic mothers could be attributed to the effect of maternal diabetes. This declined only slightly in later periods, at 76% in 1987-93 and 74% in 1994-2011.

Øyen et al say that prenatal care for diabetic women has reportedly improved over recent years, and suggest that factors such as increased rates of obesity and Type 2 diabetes "may have outweighed the effects of better prenatal care at the population level."

But editorialist Adolfo Correa (University of Mississippi Medical Center, Jackson, USA) believes the finding "raises questions about the level of awareness about the potential for prevention and/or limited availability or access to preconception care programs for women with pre-gestational diabetes."

He says the study highlights the importance of good metabolic control in diabetic women both prior to and during pregnancy.

"The potential benefits derived from such efforts will go beyond a reduction in prevalence of CHD, as they are likely to include a reduction in prevalence of a wide range of other adverse pregnancy outcomes and associated health care costs", he says.

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