INCREASE OF INCIDENCE AND RISK OF DOWNS-S YNDROME BIRTHS IN LENINGRAD(1982-1989)

Among 559 286 infants born in Leningrad in 1982 - 1989, there was reve aled 744 infants (1.33 parts per thousand) with Down's syndrome (DS). The age distribution for their mothers as well as for 79 571 parturien t women in the general population was investigated. The data regarding the period studied was compared with the results of a similar investi gation conducted during of 1945 - 1961. A decrease in maternal age in the population was demonstrated. This was more pronounced for the moth ers of affected infants. A 1.4- to 2.2-fold increase of birth risks fo r DS was found in all maternal age groups. The doubling of the risk va lue occurred by the age of 30 - 34, in contrast to 35 - 39 in 1945 - 1 961.