Obstetric and social origins of mentally handicapped children.

New and conflicting evidence about the effect of pre-natal life and the process of birth has revived the old argument about the relative importance of nature and nurture in producing cerebral defects. A few processes have received general recognition; for example, that birth trauma may cause cerebral palsy and that rubella in early pregnancy may cause certain malformations associated with impaired cerebral function. The effect of foetal anoxia, not accompanied by birth trauma, is still disputed (Darke, 1944; Illingworth, 1955; Lilienfeld and Pasamanick, 1955; Graham, Caldwell, Ernhart, Pennoyer, and Hartmann, 1957; Fraser and Wilks, 1959). Prematurity has been alternately blamed and exonerated in successive studies of the past 40 years (see Alm, 1953), a recent example being two conflicting papers from Edinburgh (Drillien, 1959; Douglas, 1960). The Baltimore workers (Lilienfeld and Pasamanick, 1954; Pasamanick and Lilienfeld, 1955) have postulated "a continuum of reproductive casualty" which signifies that in their view a wide range of obstetric abnormalities, such as pre-eclampsia, prematurity, and placenta praevia, are responsible for an equally wide range of defects in children, such as mental deficiency, epilepsy, and behaviour disorder. Recently Knobloch and Pasamanick (1959) have gone so far as to suggest that, insofar as "intellectual potential" is concerned, "all men are conceived equal". On this view all observable differences in intellectual ability are the result of pre-natal damage, the birth process, or post-natal conditions. Studies in this field are difficult to assess and to reconcile with each other. Much confusion may be attributed to imperfect definition of terms and