In 1968, Uchida et al. concluded that mothers exposed to abdominal radiological procedures run an increased risk of having a child with Down syndrome, particularly in their late reproductive years. An association between relatively high doses of maternal radiation and Down syndrome has also been reported by other workers. The authors have some evidence that diagnostic X rays may be important in the origin of a new chromosomal abnormality other than Down syndrome. Chromosome analyses have been done on 4342 children, seven or eight years old, ascertained in the Collaborative Perinatal Project. Maternal diagnostic irradiation in the year before conception and up to the third lunar month of the index pregnancy was recorded along with a large amount of family and clinical data. Information on X ray exposure was supplied by the mothers, so we cannot estimate radiation dosage. The data were recorded before the chromosome study began. 21 children (including a pair of twins and a pair of siblings) born to 19 mothers had chromosomal aberrations. Of the 13 mothers (excluding mothers of 6 children with inherited translocations, rearrangements, and XYY karyotypes), 3 (23%) had received abdominal and pelvic X ray exposures. In the whole sample, however, only 6% of the mothers had diagnostic irradiation. 2 of these mothers, aged sixteen and twenty, gave birth to a child each with de novo autosomal translocations [46,XX,t(1;2) (p22q37); 46,XY,t(5;6) (p15;q15)] and the third mother, aged thirty two, had a child with a complex mosaicism involving one X chromosome. Although the sample size of mothers with chromosomally abnormal children is small, the results are significant.
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