Chromosome studies in 5,049 consecutive newborn children

Data from a chromosome examination of 5,049 consecutive newborn children are presented. Major chromosome abnormalities were found in 43 (0.85 %) children. Only 6 of the 43 children were phenotypically abnormal to the extent that they could be diagnosed clinically; these six comprised a girl with Turner's syndrome, a boy with Patau's syndrome and four boys with Down's syndrome. It was remarkable that two male infants with karyo‐types 46,XY,12p‐ and 46,XY/46,XY,5p‐ were normally developed. Chromosome variants (marker chromosomes) occurred in 87 (1.72 %) of the children. The most common marker chromosomes were Yq+, Yq‐, Dp+ or Ds+ and Gp+ or Gs+ very little is known about the significance of marker chromosomes. Chromosome examination in newborn children gives the possibility of procuring incidence figures, finding families with translocations, studying segregation rates and giving genetic advice. Follow up studies of children with chromosome abnormalities and marker chromosomes compared with controls as well as treatment of children with chromosome abnormalities whenever possible are also important aspects of such studies.