During the period from 1961 - 1997 the prevalence of Down’s syndrome (DS) was followed up on the territory of the Czech Republic. From a consecutive series of 5 319 002 births in the CR during 1961 - 1997 4 933 cases of DS were diagnosed, incl. 4 410 in born infants and 523 were diagnosed prenatally and these pregnancies were terminated. The mean incidence of DS in born children during the investigation period was 7.91 per 10 000 liveborn infants. When the results of prenatal diagnosis of DS are added the mean incidence was 9.47 per 10 000 liveborn children. The prenatal diagnosis of DS in the CR was also investigated. The success rate of prenatal diagnosis of DS in the CR increased during the period from 1980 - 1997 to as much as 60% of detected cases. In 37.31% of all cases of Down’s syndrome another inborn defect was found, most frequently inborn heart disease, defects of the central nervous system, gastrointestinal and urogenital tract. The age distribution of DS indicates a significantly increased risk for mothers already from the age of 34 years.

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