Why is Down syndrome associated with congenital cardiac abnormalities in many children?

Down syndrome is a congenital disorder caused by the presence of extra genetic material from chromosome 21, a condition known as trisomy 21. This chromosomal abnormality is a significant factor in the development of congenital heart disease, which affects approximately 40 to 60 percent of individuals with Down syndrome.12

The association exists because Down syndrome is a chromosomal abnormality that disrupts normal embryonic development. The heart undergoes a complex evolution during this period, and the presence of the extra chromosome interferes with these developmental processes, leading to various cardiac malformations. While the exact molecular mechanisms remain a subject of ongoing research, it is established that these genetic alterations frequently result in structural heart defects. Because these defects are congenital, they are present at birth and are often identified through clinical evaluation, such as the detection of a cardiac murmur.21