What percentage of individuals with Down syndrome have congenital heart disease?

• A. 25%
• B. 50%
• C. 75%
• D. 10%

Answer: (B)

Down syndrome is strongly associated with congenital heart defects, so a large portion of affected individuals have some cardiac anomaly. The typical teaching value is that about half of people with Down syndrome have a congenital heart defect, with studies often reporting a range around 40% to 60%. This is why the around-50% figure is the best choice. The most common defect in this group is an atrioventricular septal defect, though other lesions like atrial or ventricular septal defects can occur. The other percentages are outside this usual range, either underestimating or overestimating the true prevalence.