[Incidence and significance of chromosomal translocations in prenatal diagnosis]

In the study reported here the incidence and significance of translocations in antenatal diagnosis are described with reference to data of the cytogenic laboratory of Cologne University Gynecological Clinic. During the last 10 years 19 translocations were found in 4532 amnion cell cultures (0.44%), without exception in single pregnancies. In 18 cases the chromosome aberrations were balanced, i.e., the location of the genetic material was changed without loss or addition of parts of chromosomes. In one case the diagnosis of an unbalanced translocation in the form of a translocation mongolism led to termination of pregnancy. All of the other pregnancies were continued to term. Phenotypically and clinically the children were normal. The translocations were inherited in 78.9% (n = 15; 11 from the mother, 4 from the father), and de novo in 21.1% (n = 4). The results are in agreement with those of the DFG study, which identified 0.66% translocations in over 10,000 antenatal diagnoses. Of the balanced chromosome aberrations all of the newborns but one were clinically and phenotypically healthy. In cases of inherited translocations in particular, no increase in risk to the child could be determined. In cases of de novo chromosome aberrations there is a slight increase in the residual risk due to loss of minute portions of the gene. With careful technique this risk may be assumed to be very slight, so that in such cases also there is no indication for termination of pregnancy.