[Prevalence of severe mental retardation and trisomy 21 in 3 generations: 1972, 1976, and 1981].

With the aim of studying whether improved prenatal and perinatal care would lead to a decrease in the prevalence of severe mental retardation and/or in Down syndrome, handicapped children born in 1972, 1976 and 1981 and residing in 14 French "departements" were systematically registered in 1985-86 and 1989 in collaboration with the "Commissions Départementales de l'Education Spéciale" (CDES), which centralizes requests for specialty services. The findings showed a stable rates of Down's Syndrome (0.7 p. 1000 in 1972, 0.8 p. 1000 in 1976 and 0.9 p. 1000 in 1981) and of severe mental retardation (1.6 p. 1000 in 1972, 1.5 p. 1000 in 1976 and 1.6 p. 1000 in 1981) in the three generations among children below the age of 9 years. The survey shows that implementation of perinatal health care programs starting in the 1970s, had not been followed by a decrease of severe mental retardation prevalence or Down syndrome prevalence across the three generations 1972, 1976 and 1981.