[Genetic counseling of parents with children with clefts].

The elucidation of the aetiology of the individual case has proved to be of fundamental importance to the counselling interview as well as to the assessment of the risk for further affected children. Up to now, a genetic cause in the form of chromosomal or gene mutations can be assumed only if the cleft is related to a distinct syndrome. An isolated cleft obviously owes its origin to a combination of genetic and extrinsic factors. Consequently, the assessment of the risk of repetition is to a great extent based on empirical values.