【目的】 分析先天愚型患儿的额外21号染色体的双亲来源和部分环境因素与先天愚型的相关性。 【方法】 1)应用染色体核型分析技术确定患儿及双亲的染色体核型;2)应用短串联重复序列连锁分析(STR-PCR)技术分析额外21号染色体双亲来源;3)通过问卷调查分析父母的环境因素。 【结果】 1)在297例先天愚型中三体型、易位型和嵌合型分别占90.2%、5.4% 和4.4%。其中男性191例,女性106例,男女比为1.8∶1。患儿就诊年龄在1个月内为23%,1岁内63%,3岁内80%,6岁内达到92%。2)在22例能提供遗传信息的家系中母亲来源的21号额外染色体共21例,占 95%(21/22),其中14例能够明确是来源于母亲卵细胞的第一次减数分裂不分离;父亲来源的21号额外染色体仅有1例,占5%(1/22)。3)80例患儿中有71例的母亲生育年龄＜35岁,占88.8%(71/80),仅有9例患儿的母亲生育年龄≥35岁,占11.2%(9/80)。父亲吸烟和饮酒在先天愚型组与对照组间的差异无统计学意义(P均>0.05);父母亲化学物质接触在两组间的差异有统计学意义(P均＜0.05)。 【结论】 1)先天愚型的额外21号染色体主要来源于母亲;2)母亲生育年龄不是我国现阶段先天愚型出生的主要因素。3)父亲吸烟和饮酒、父母亲化学物质接触似乎与先天愚型的发生没有直接的关联。

【Objective】 To analyze the parental origin of the extra 21^st chromosome of patients with Down's syndrome (DS) and the correlation between the partial environmental factors and DS. 【Methods】 1)The chromosomal karyotypes of patients and their parents were determined by karyotype analysis technique. 2)The parental origin of extra 21^st Chromosome in DS patients were confirmed by short tandem repeat polymerase chain reaction(STR-PCR). 3)The environment factors in parents were surveyed through the retrospective questionnaire. 【Results】 1)Among 297 DS patients, the karyotypes of trisomy, translocation and mosaic accounted for 90.2%, 5.4% and 4.4%, respectively. 2)Clinical analysis: Among 297 DS patients, there were 191 males (64.3%, 191/297) and 106 females (35.7%, 106/297), with a sex ratio of 1.8∶1 (191∶106). The patients whose age at diagnosis were within one month, within one year and within six years accounted for 23%, 63% and 92%, respectively. 3)The 21^st extra chromosome origin analysis: The genealogy of genetic information by STR linkage analysis in 22 cases displayed that the 21^st extra chromosomes of 21 cases were originated from mothers, amounting for 95% (21/22). Among them, 14 cases were caused by the first division nondisjunction of ovum in patients'mothers. Only one case was originated from the father, accounting for 5% (1/22). 4)Environmental factors investigation in parents: the age of 71 mothers who gave birth were below 35 years old, accounting for 88.8% (71/80). And only 9 mothers were equal to or over 35 years old, accounting for 11.2% (9/80) (P＞0.05). There was no statistically significant difference in smoking and drinking between the father group of DS patients and control group. However, statistical significance could be observed between the two groups in exposure to chemical materials of the parents (P＜0.05). 【Conclusions】 1)The majority of extra 21^st Chromosome of DS patients are originated from their mothers. 2)At present, age of a mother giving birth is not main factor for Down's syndrome. 3)Smoking and drinking of father, exposure to chemical materials of parents seem not to be directly related to the Down's syndrome.