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随着母亲年龄增长,Down氏综合征婴儿出生的危险率显著增加。从存活婴儿的调查得知,母亲年龄在35岁以上者,其婴儿发生Down氏综合征的危险率约为千分之六。年龄在35—39岁者,危险率约为0.4％,40—44岁者约为1.2％,45岁以上者约为4％。由于早期产前诊断有效性增加,从羊膜穿刺资料得到的Down氏综合征的危险率要比存活婴儿调查资料得到的危险率高。根据羊膜穿刺所得结果,Down氏综合征的危险率在35—39岁年龄组是0.55—1.4％,40—44岁年龄组是2.7—5.8％。然而,在第三届
As mothers age, the risk of Down’s syndrome infants born significantly increased. According to a survey of surviving infants, the risk of Down’s syndrome in a baby whose mother is over 35 years of age is about six thousandths. The risk is about 0.4% for those 35-39 years of age, about 1.2% for those 40-44 and about 4% for people over 45 years of age. Due to the increased effectiveness of early prenatal diagnosis, the risk of Down’s syndrome from amniocentesis is higher than that from surviving infants. According to the results of amniocentesis, the risk of Down’s syndrome is 0.55-1.4% in the 35-39 age group and 2.7-5.8% in the 40-44 age group. However, in the third