Down syndrome and maternal age in Japan, 1950-1973

Abstract

The mean maternal age and the percentage age distribution of 2650 mothers of children with Down syndrome were calculated for 1950-1973, from hospital records. Mean maternal age has dropped both for controls (28.55-27.37) and Down syndrome (31.26-29.59). The observed maternal age distributions were very similar to those expected in corresponding periods. The fall in maternal age in Down syndrome in recent years has resulted from the general trend to decreasing maternal age. There has been no change in the age-specific incidences of Down syndrome. The incidence of Down syndrome seems to be falling in Japan.