Down syndromeMedical Conditions
Down syndrome is the most common birth defect, caused by 3 copies (trisomy) of Chromosome 21. Children with Down syndrome have a flattened nose and eyes that slant upward. They have short, broad fingers and may have a single crease in the palm. Most children with Down syndrome are developmentally delayed and don't reach average adult height. Many have heart defects and problems with the digestive tract.