The predictive value of microcephaly during the first year of life for mental retardation at seven years.

Of 41 term infants surviving to seven years of age with head circumferences (HC) - 3 SD, 21 were mentally retarded (IQ less than or equal to 70) at seven years. HC - 2 SD was associated with mental retardation in 11 per cent of children. Socio-economic status did not affect mental outcome of children with HC - 3 SD, but higher socio-economic level was associated with better outcome for those with HC - 2 SD or who were normocephalic. Mental retardation in children with HC - 3 SD was more common in children with additional pathology. Of 25 children with no other pathology, one-quarter were mentally retarded at seven years; this was more common in children of normal birthweight. Disproportionate head-to-height ratio did not significantly affect outcome, although short stature was associated with less favourable outcome for those with HC - 2 SD or who were normocephalic.