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Down syndrome is the most common autosomal chromosomal abnormality characterized by mental and growth retardation, and by various typical features including prominent epicanthal fold, oblique palpebral fissure, flat nasal bridge, short and broad hand, wide toe interspace, etc. The overall incidence has been shown to be 1:800 deliveries, increasing with advancing maternal age. However, twin cses are extremely rare, and... |
