Frequency of down syndrome in livebirths by single-year maternal age interval: Results of a Massachusetts study

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Abstract
An analysis of rates of intra‐state Down syndrome livebirths to Massachusetts residents by single‐year maternal age interval in 1958‐1965 inclusive was carried out. A gradual increase of rate of the Down syndrome occurred from age 20 to about age 31, and a steeper increase thereafter. Different regression equations were derived in the 20‐31 and the 33‐45 age group. The regression equations were In y = 0.04515 x −1.45759 for those age 20‐31 and ln y = 0.24302 x −7.57870, for those age 33‐45, where y = rate per 1,000 and x = maternal age. The regression‐derived rates are slightly lower than those reported in similar analyses of data from Sweden and New York State, but they are not markedly discrepant.