1991年10月至1997年6月通过遗传咨询观察了智力低下（MR）儿童1680例，其中男性占53．3％，女性占46．7％；伴癫痫者占11．2％，伴脑瘫者占21％，第一胎占82．6％，轻度MR占73．8％，中度MR占22．9％，重度MR占3．3％，染色体核型异常检出率为14．6％．其中常染色体异常占73．1％，性染色体异常占26．9％，在病因探讨中，属于出生前因素占41．2％．出生时因素占26．5％，出生后因素占2．7％，原因不明占29．6％。 From October 1991 to June 1997, 1680 children with mental retardation (MR) were observed through genetic counseling, of which 53.3% were male and 46.7% were female; 11.2% had epilepsy with cerebral palsy Accounting for 21%, first birth accounted for 82.6%, mild MR accounted for 73.8%, moderate MR accounted for 22.9%, severe MR accounted for 3.3%, chromosome karyotype abnormality detection rate was 14.6 %. Of them, autosomal abnormalities accounted for 73.1%, sex chromosome abnormalities accounted for 26.9%, in the etiological study, belong to prenatal factors accounted for 41.2%. 26.5% at birth, 2.7% at birth, and 29.6% for unknown reasons.