A SEX CHROMATIN AND Y BODY SURVEY OF TORONTO NEWBORNS

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Abstract
Sex chromatin determinations were performed on the amniotic membranes of 72,739 newborns in 11 Toronto hospitals. These analyses, carried out between I October 1967 to 31 May 1971, identified 40 XXY subjects, 16 XXX, 1 XO, 1 XXYY as well as 9 mosaics of various constitutions. A further five subjects with normal karyotypes but discrepant phenotypic sexes were found in this population. 1735 of the males (of the above) were also examined for fluorescent Y bodies. An additional 3660 males, born between 1 June 1971 and 30 September 1971, were examined for Y bodies only. Five XYY newborns were identified by the Y body screening as well as one XY/XXY and three more XXY subjects. Incidence figures for the various sex chromosome aberrations were not significantly different from similar figures derived from other studies. A not unexpected maternal age effect on the incidence of X chromosome abnormalities was demonstrated, older mothers having a higher risk. A pronounced parity effect was noted, first born offspring having a greater risk. A seasonal variation in the incidence of XXY births was found; a peak in the incidence during the spring months, followed by a minor second peak in the autumn.