目的分析21三体综合征患者的染色体核型,探求病因,提出预防与遗传咨询策略。方法常规外周血淋巴细胞培养方法制备染色体标本,G显带技术进行细胞遗传学分析和遗传咨询。结果 26例确诊的21三体综合征染色体核型中,单纯型23例(占88.46%),嵌合型1例(占3.85%),易位型2例(占7.69%);26例患儿的母亲在生育患儿时的年龄>35岁6例(占23.08%),父亲年龄>39岁5例(占19.23%);26名患儿中有1位易位型患儿的母亲为罗伯逊平衡易位携带者。结论 21三体综合征是造成小儿先天智力障碍的重要原因,其中单纯型比例最高,易位型和嵌合型较少;其发生与父母年龄、遗传和环境因素相关。细胞遗传学分析是诊断21三体综合征必不可少的方法;产前筛查和遗传优生咨询是降低21三体综合征患儿出生率、提高人口素质的有效手段。 Objective To analyze the chromosome karyotype of patients with trisomy 21 and explore the cause of the disease and put forward the preventive and genetic counseling strategies. Methods Chromosome specimens were prepared by routine peripheral blood lymphocyte culture method, and G - banding technique was used for cytogenetic analysis and genetic counseling. Results Twenty-six cases of trisomy 21 were detected in 23 cases (88.46%), in 1 case (3.85%), in 2 cases (7.69%), in 26 cases The mothers of children aged 35 years and older were 6 (23.08%) and their father was 39 years old (19.23%). One of the 26 children had a translocation mother Robertson balance translocation carriers. Conclusion Trisomy 21 is an important cause of congenital mental retardation in children, of which the highest proportion of simple type, less translocation and chimerism; its occurrence and age, parents, genetic and environmental factors. Cytogenetic analysis is an indispensable method for the diagnosis of trisomy 21. Prenatal screening and genetic counseling are effective ways to reduce the birth rate and improve the quality of the population in trisomy 21 patients.