Connor J M, Ferguson-Smith M A
Baillieres Clin Obstet Gynaecol. 1988 Mar;2(1):37-54. doi: 10.1016/s0950-3552(88)80062-2.
Prior to 1970 nearly one half of severe mental handicap (IQ less than 50) was unexplained and genetic causes were recognized in one third of all patients. In recent years the genetic contribution has risen to 50%, with the decline in importance of environmental causes and the growing recognition of X-linked forms of mental retardation and chromosomal microdeletion syndromes. Recognition of genetic conditions is vital for accurate assessment of recurrence risks and in order, in some instances, to provide specific prenatal diagnosis. With full utilization of existing prenatal screening procedures and a more detailed family history, severe mental handicap due to genetic conditions should be reduced by 30-40%.
1970年以前，近一半的重度智力障碍（智商低于50）病因不明，三分之一的患者被认为是由遗传因素导致。近年来，随着环境因素重要性的下降以及对X连锁智力障碍形式和染色体微缺失综合征的认识不断增加，遗传因素导致的智力障碍比例已升至50%。识别遗传疾病对于准确评估复发风险至关重要，并且在某些情况下可以进行特定的产前诊断。充分利用现有的产前筛查程序并获取更详细的家族病史，遗传因素导致的重度智力障碍应可减少30%至40%。
