A young Asian boy holding a red heart in both hands to symbolize heart shape and links with congenital heart defect (CHD)
Credit: krisanapong detraphiphat/Getty Images.

Results from a large Finnish study show that women with type 1 diabetes are almost four times more likely to have a baby with a congenital heart defect (CHD) than those without diabetes.

This association confirms previous research showing a link between maternal type 1 diabetes and CHDs in offspring.

As reported in the journal JAMA Network Open, the researchers also found that risk of some forms of CHD were also increased in children of overweight and obese women, but to a lower level than that associated with type 1 diabetes.

CHDs are a common birth defect and are thought to occur in about one in 100 newborns. Many children with a CHD survive to adulthood and are able to live relatively normal lives, but CHDs can cause significant health issues and often require surgery.

While some of the risk associated with these congenital conditions is genetic, it is possible some environmental factors could be modifiable and that the risk for CHDs could be reduced in future.

In this study, lead author Riitta Turunen, a clinician and researcher from the University of Helsinki, and colleagues analyzed data from 620,751 children born in Finland between 2006 and 2016 and 573,259 mothers aged 20–40 years. Of the children born during this period, 10,254 had a CHD.

Turunen and team assessed the diabetes and weight status of the mothers included in the study. Overall, around 0.7% of the mothers had type 1 diabetes, 10–20% had gestational diabetes and 0.1–0.3% had type 2 diabetes. Up to 22% of mothers were overweight and up to 11% were obese in the cohort.

After correcting for a range of possible confounding factors, having type 1 diabetes increased the chances of having a child with any CHD by 3.77-fold compared with no maternal diabetes and the chances of having a child with six of nine individual CHD subgroups by 3.28–7.29-fold.

Being overweight increased the risks of left ventricular outflow tract obstruction by 28% versus normal maternal weight and maternal obesity increased the risk of complex defects and right outflow tract obstruction by 2.70- and 1.31-fold, respectively, versus having a normal body mass index.

Notably the effects of type 1 diabetes and overweight and obesity on CHD risk did not seem to be linked.

“These different risk profiles of type 1 diabetes and overweight and obesity may suggest distinct underlying teratogenic mechanisms,” write the authors.

“Maternal overweight and obesity were associated with a smaller increase in risk, at least in this high resource setting with universal antenatal care. However, with increasing prevalence of… maternal overweight, the risk at the population level is substantial,” they add.

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