pediatrics
Down Syndrome (Trisomy 21)
Introduction
Down syndrome is an abnormality of chromosome 21 that can cause Intellectual Disability , microcephaly, short stature, and characteristic facies. Diagnosis is suggested by physical anomalies and abnormal development and confirmed by cytogenetic analysis. Management depends on specific manifestations and anomalies. (See also Overview of Chromosomal Abnormalities .) Overall incidence in the United States is approximately 1/700 live births ( References ), and the risk increases gradually with increasing maternal age. Based on a large study, at 20 years of maternal age, the risk is 1/1466 births; at 35, it is 1/343; and at 40, it is 1/85 ( 