Pre- and perinatal hazards and family background in children with specific language impairments: a study of twins.
A clinical group composed of 84 twin pairs where one or both twins met stringent psychometric criteria for specific speech-language impairment was compared with 36 twin pairs with no history of speech-language difficulties. Twins with speech-language impairment tended to have more siblings than control twins and were significantly more likely to have an affected parent. Groups were closely similar in terms of length of gestation and mother's antenatal condition, except that maternal toxemia was unusually frequent in the clinical group. Children from the two groups did not differ in terms of Apgar scores or on a composite measure of perinatal hazards. Within the clinical group, MZ pairs with substantial differences in neonatal status did not differ in language outcome. It is suggested that if an association with toxemia can be replicated, this might reflect a common genetic basis for immune disorders and developmental language delay. Perinatal hazard was unrelated to subtype of speech-language impairment.