BACKGROUND:

As a result of antenatal screening, abortion of fetuses with Down syndrome has become increasingly common. Little is known about the cardiovascular phenotype in infants with Down syndrome born today.

METHODS:

Population-based cohort study based on national health registers including 2588 infants with Down syndrome, live-born in Sweden from 1992 to 2012. Risk ratios for congenital heart defects were calculated per 3-year period, adjusted for maternal age, parity, BMI, smoking, diabetes and hypertensive disease, and infant gender.

RESULTS:

Any congenital heart defect was diagnosed in 54% of infants with Down syndrome. Overall, year of birth was not associated with risk of any congenital heart defect. However, the risk of complex congenital heart defects decreased over time. Compared with 1992 to 1994, the risk in 2010 to 2012 was reduced by almost 40% (adjusted risk ratio 0.62, 95% confidence interval 0.48–0.79). In contrast, risks for isolated ventricular septal defect (VSD) or atrial septal defect showed significant increases during latter years. Overall, the 3 most common diagnoses were atrioventricular septal defect, VSD, or atrial septal defect, accounting for 42%, 22%, and 16% of congenital heart defects, respectively. Although atrioventricular septal defect was far more common than VSD in 1992 to 1994, they were equally common in 2010 to 2012.

CONCLUSIONS:

Complex congenital heart defects have become less common in infants diagnosed with Down syndrome. This phenotypic shift could be a result of selective abortion of fetuses with Down syndrome, or due to general improvements in antenatal diagnostics of complex congenital heart defects.

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