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Maternal Type 1 Diabetes Drives Congenital Heart Defects

Researchers published the study covered in this summary on MedRxiv as a preprint that has not yet been peer reviewed.

Key Takeaways

  • Maternal type 1 diabetes significantly linked with a 3.7-fold increased rate of congenital heart defects (CHD) in their children, by far the strongest maternal risk factor associated with this outcome, in a retrospective review of prospectively collected, nationwide data from Finland.

  • The results also showed weaker associations between maternal overweight and obesity and CHD in offspring than previously reported, perhaps because of the comprehensive data collected on maternal diabetes. The effect of diabetes appeared to account for a larger part of the risk seen in mothers with overweight or obesity than previously estimated.

  • Gestational diabetes mellitus (GDM) and maternal type 2 diabetes each associated with smaller increased rates of CHD. Nonetheless, increasing prevalence of both GDM and maternal overweight produces a substantial overall population risk.

Why This Matters

  • Congenital heart defects affect 1%-2% of newborns and are associated with significant mortality and morbidity.

  • The role of maternal type 1 diabetes as a significant risk factor has been well documented, but the significance of maternal obesity and overweight has been less clear.

  • The results suggest that maternal diabetes and maternal overweight or obesity may have distinct teratogenic mechanisms, as the associations were different for several CHD subgroups, and in some cases went in opposite directions.

  • Understanding the risk factors underlying CHD is essential for prevention. 

Study Design

  • The retrospective study used data collected prospectively in several Finnish national registries and included 620,751 children born during 2006-2016 and their mothers, including 10,254 children (1.6%) with an isolated CHD.

  • The main outcome assessed was isolated CHD, defined as a diagnosis for one or more CHD and not having diagnoses for chromosomal aberrations, syndromes, or any other major extracardiac anomalies. Isolated CHD were divided into nine groups based on their anatomical presentation.

Key Results

  • During the 11-year study period, GDM prevalence increased from 10.3% to 19.2%, type 2 diabetes prevalence increased from 0.1% to 0.3%, and prevalence of type 1 diabetes remained roughly unchanged at about 0.7%.

  • Maternal overweight prevalence increased from 20.3% to 22.2% and maternal obesity increased from 10.7% to 13.3%.

  • In a multivariable analysis that adjusted for several potential confounders, maternal type 1 diabetes significantly associated with a 3.7-fold increased prevalence of any CHD in their offspring. The prevalence of any CHD was a significant twofold higher among children born to mothers with type 2 diabetes (odds ratio, 2.01; 95% CI, 1.34 – 3.03; P < .001).  

  • No significant association existed between maternal obesity or overweight and isolated CHD in the offspring.

  • Further analyses also showed significant associations between type 1 diabetes, type 2 diabetes, and overweight and obesity and several specific types and subgroups of CHD.

  • Further analysis also showed that having diabetes significantly linked with a 17.2% population attributable risk for having a child with any CHD among mothers with diabetes. Among all the mothers studied, having diabetes significantly linked with a 3% population attributable risk for CHD.


  • The number of offspring in the various CHD subgroups was relatively limited.

  • The study lacked reliable data on pregnancy terminations and miscarriages, which often involve CHD.


  • The study received no commercial funding.

  • None of the authors had disclosures.

This is a summary of a preprint research study, “Maternal diabetes and overweight as risk factors for congenital heart defects in offspring – A nationwide register study from Finland,” by researchers from several centers in Finland, Sweden, Norway, and Canada, published on MedRxiv, provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found on

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