Chromosome examination of children, in two Danish counties, born during the period 1967-1978

The investigation comprises children in two Danish counties, Viborg and Ringkøbing, born during the period 1967–1978, in whom a chromosome abnormality or a chromosome variant has been found. The incidence of Patau's syndrome (+13) and Edwards' syndrome (+18) was 0.18 per 1,000 in these two counties, compared with an expected incidence of 0.24 per 1,000. The incidence of Down's syndrome was 1.02 per 1,000, compared with an expected incidence of 1.15 per 1,000; none of the differences are significant. The incidence of other chromosome abnormalities than the above-mentioned was on the same frequency level in Ringkøbing and Viborg counties as in the rest of the country and significantly lower than the expected incidence. Even if one cannot expect that all these chromosome abnormalities can be diagnosed, it would most probably be possible to diagnose chromosome abnormalities in more of these children than has previously been the case, especially in children with sex chromosome abnormalities if one is more alert concerning such conditions.