Mikkelsen M
Department of Medical Genetics, John F. Kennedy Institute, Copenhagen, Denmark.
Philos Trans R Soc Lond B Biol Sci. 1988 Jun 15;319(1194):315-24. doi: 10.1098/rstb.1988.0053.
Down's syndrome is the most common autosomal aberration and single cause of mental retardation in man. There is a close relation between advanced maternal age and Down's syndrome. The limitation of family size has made a considerable impact on the incidence of Down's syndrome. In Denmark in the 1950s, 50% of Down's syndrome cases were born to mothers over the age of 35. The percentage went down to 25% in the 1970s and was reduced by prenatal diagnosis to 8% in the 1980s. For the period 1980-85 we followed the birth prevalence closely for different maternal age groups. The birth prevalence was lowered for the age group over 35, but there was a steady rise for the age groups below 35. Early diagnosis, high rate of survival of light-for-date babies and babies with congenital heart defect, and, possibly, exogenous factors working on gametogenesis might be an explanation. To achieve a reduction in incidence, maternal alpha-fetoprotein (AFP)-serum screening for low values may be a possibility. So far, avoidance, but not primary prevention, of Down's syndrome is available.
唐氏综合征是人类最常见的常染色体畸变，也是导致智力迟钝的单一原因。母亲年龄偏大与唐氏综合征之间存在密切关系。家庭规模的限制对唐氏综合征的发病率产生了相当大的影响。在20世纪50年代的丹麦，50%的唐氏综合征患儿母亲年龄超过35岁。这一比例在20世纪70年代降至25%，到20世纪80年代通过产前诊断又降至8%。在1980 - 1985年期间，我们密切跟踪了不同母亲年龄组的出生患病率。35岁以上年龄组的出生患病率有所降低，但35岁以下年龄组则呈稳步上升趋势。早期诊断、足月小样儿和先天性心脏病患儿的高存活率，以及可能作用于配子发生的外源性因素或许可以解释这一现象。为降低发病率，对母体血清甲胎蛋白（AFP）低值进行筛查可能是一种办法。到目前为止，能够做到的是避免唐氏综合征的发生，而非一级预防。
