先天愚型是一种胚胎性脑发育障碍性疾病，其发病率约占新生儿的1／650。据资料统计，40岁以上妊娠母亲出生的婴儿发病率高于25～30岁年龄组10倍。主要病因是受精卵在减数分裂过程中出现不分裂或障碍所致。本文收集1983～1993年17例小儿先天愚型骨盆X线片，结合临床资料和染色体 Down’s syndrome is an embryonic brain developmental disorder, the incidence of about 1/650 of the newborn. According to statistics, the incidence of babies born pregnant mothers over the age of 40 is 10 times higher than the 25-30 age group. The main cause is fertilized eggs in the process of meiosis did not divide or obstacles caused. This article collected from 1983 to 1993 17 cases of children’s Down’s pelvis X-ray, combined with clinical data and chromosomes