4 - 6% of the liveboms are affected with some form of congenital disease (Warkany, 1971; Trimble & Doughty, 1974). Accordingly, in The Netherlands each year 8000 - 12.000 children are born with a more or less severe handi­cap. In some cases morphological and/or functional abnormalities are apparent shortly after birth, as is the case in anencephaly, meningomyelocele, conge­nital heart defects, several chromosomal aberrations and inborn errors of meta­bolism. In other congenital diseases the onset of clinical manifestations occurs in early or late childhood and some sex-chromosomal aberrations will not be detected before puberty.

Finally, a number of these diseases is not manifest before adulthood, like Huntington's chorea and a number of variants of inherited metabolic disorders. The three main categories of congenital diseases are:

1 . Chromosomal aberrations, with an incidence of 1 : 200 liveborns (Jacobs et al., 1974); about 1000 patients per year in The Netherlands.

Read the rest of this entry »