Ｄｏｗｎ综合征(Ｄｏｗｎ’ｓｓｙｎｄｒｏｍｅ,ＤＳ)是人类最常见、最重要的先天性疾病之一,新生儿发病率约为1/7001000[1],占小儿染色体病的70%。多数病例是由患者体内所有细胞中21号染色体三体引起的,较少病例是由于体内部分细胞21号染色体三体(嵌合体)或21号染色体部分三体 Down syndrome (DS) is one of the most common and important congenital diseases in humans. The incidence of neonatal morbidity is about 1/7001 000 [1], accounting for 70% of pediatric chromosome disease. Most cases are caused by trisomy 21 chromosomes in all cells of the patient, and fewer cases are due to trisomy 21 (trisomy 21) or trisomy 21