[Maternal and perinatal antecedents of encephalopathies: their contribution to a trial classification of encephalopathies of unknown origin].

We had a sample of 135 mentally retarded children, whose case history (maternal, obstetrical and perinatal) was known before their mental retardation was suspected. This analysis made it possible to pinpoint characteristic anamnesic giving rise to mental retardation by comparison with a check population. It appears that these factors differ according to the supposed origin of mental retardation (genetic, embryonic, foetal, perinatal and postnatal periods) therefore, they can be considered "explicative" of these origins. A multivariate analysis of these factors indicates that the majority of cases of mental retardation with unknown origin are due to disorders during foetal life, which had not been detected.