Differences in maternal age‐specific rates of down syndrome between Jews of European origin and of north African or Asian origin

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Abstract
Rates of Down''s syndrome in livebirths in West Jerusalem in 1964-1975 were studied in relation to the mother''s continent of birth or, if she was born in Israel, to the maternal grandfather''s continent of birth. In women of European origin the crude livebirth rate of Down''s syndrome was 1.3 per 1000 livebirths. This crude rate and the maternal age-specific rates in this group were very close to those observed in a Swedish study and 2 studies of white livebirths in the USA. For West Jerusalem women of North African or Asian origin the crude rate was about 2.4 per 1000 livebirths, and at all maternal ages except the youngest their rates were higher than for women of European origin. The summary adjusted relative risk for a Down''s syndrome livebirth for all those of North African or Asian origin, compared to those for women of European origin, was about 1.56. If attention is restricted to mothers born outside of Israel, the adjusted relative risk for mothers born in Europe, the Americas or English speaking countries of the British commonwealth compared to those born in North Africa or Asia was 1.97, consistent with a 2-fold difference in the likelihood of a Down''s syndrome livebirth between these 2 groups. This is apparently the 1st report of ethnic differences in maternal age specific rates of Down''s syndrome that cannot be plausibly explained by differences in ascertainment.