More congenital heart defects due to maternal diabetes

Diabetes and obesity during pregnancy increase teratogenic malformations risks. Their role in congenital heart defects was investigated in a Finnish registry study.

Data from 10 years analysed

This is a nationwide population-based register study.
All newborns in Finland between 2006 and 2016 and their mothers were included.
Women's pre-pregnancy BMI was categorised as underweight (< 18.5 kg/m2), normal weight (18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2) and obese (≥ 30 kg/m2).
For maternal diabetes, a distinction was made between type 1, type 2 and gestational diabetes.
Congenital heart defects as a whole and nine anatomical subgroups were examined.

Greatest risk in type 1 diabetes

Of the 620,751 newborns included, 10,254 (1.65%) had a congenital heart defect. Children born to mothers with type 1 diabetes (T1DM) were most at risk, with an almost four-fold increased risk. Maternal type 2 diabetes (T2DM) roughly doubled the risk, while gestational diabetes and increased weight alone were not risk factors.

Overweight should not be underestimated

A closer look at the individual heart defects reveals a different picture, which underlines the role of weight: maternal obesity was frequently associated with complex defects and malformations of the left ventricular outflow tract; maternal obesity was associated with complex defects and malformations of the right ventricular outflow tract.

Gestational diabetes on the rise

The authors suspect different molecular pathomechanisms that lead to malformations of the heart in diabetes and obesity. One thing is clear to them: an increased BMI during pregnancy is not without danger. While only 8.2% of normal-weight pregnant women developed gestational diabetes, 21.1% of overweight women and as many as 41.1% of obese women did. And this with increasing prevalences: During the study period, the proportion of pregnant women with gestational diabetes increased from 10.3% to 19.2%.

The study authors conclude that although gestational diabetes and obesity alone were not associated with an increased rate of congenital heart defects overall, the increasing prevalence at the population level nevertheless means a growing risk for the unborn child.

Conclusion for medical practice

Diabetes, especially T1DM, is associated with a significantly increased risk of congenital heart defects. In overweight and obesity, the association is less pronounced and limited to individual anatomical subgroups of heart defects. Overall, heart defects in newborns could be avoided in many cases with primary prevention of overweight/obesity and systematic treatment of diabetes during pregnancy.

Source:

Turunen R, Pulakka A, Metsälä J et al. Maternal diabetes and overweight as risk factors for congenital heart defects in offspring - A nationwide register study from Finland. MedRxiv 2023; DOI: 10.1101/2023.02.14.23285825