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We tabulated associated birth defects seen in 2894 infants
with Down syndrome and found:
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Heart defects are the most frequent associated
defect, affecting 56% of cases. The most common type is
atrioventricular canal/endocardial cushion defects, seen
in 17% of cases—1000 times more frequently than in
babies without Down syndrome. |
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About 11% have defects of the gastrointestinal tract.
Duodenal atresia—found in about 5%— is 265 times
more common in babies with Down syndrome than in the general
population.  |
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There is substantial overlap between heart
and gastrointestinal defects. For example, 86% of infants
with duodenal atresia also have heart defects. |
RISK FACTORS FOR ASSOCIATED DEFECTS
Serious structural birth defects occur in many but not all
infants with Down syndrome. Do environmental factors-interacting
with the developmental instability caused by the extra chromosome-influence
which babies have associated abnormalities? We interviewed
mothers of 687 infants with Down syndrome to answer this question
for heart and gastrointestinal defects.
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4.2% of these mothers drank 4 or more cups
of coffee daily; they had a 6 times higher chance of having
a baby with Hirschsprung disease. |
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12% of mothers smoked during the first trimester. Their
babies had double the risk for heart defects compared
to babies of nonsmokers. |
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Several factors were not associated with
any Down syndrome-associated defect:
- Fever
- Alcohol use
- Mother's age. |
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