EXPERIENCES WITH RISK ESTIMATES FOR CARRIERS OF CHROMOSOMAL RECIPROCAL TRANSLOCATIONS

The risk estimates for individual carriers of ten different familial r eciprocal translocations detected among 500 couples with reproductive failures are presented. These were established by application of the e mpirical data analysed by Stengel-Rutkowski et al. (1988) and the guid elines given in Stene & Stengel-Rutkowski (1988). Different risks were estimated for unbalanced offspring at birth or at second trimester pr enatal diagnosis for abortions, or stillbirths/early deaths. These ris k estimates varied considerably from translocation to translocation. C arriers of five translocations had risks for offspring with single-seg ment imbalances. The birth risk figures ranged from 0.1% to 13.8%. Car riers of five other translocations had risks for double-segment imbala nces with birth risks ranging from 0% to 3.2%. The estimated risk figu res were independent of the method of ascertainment. Among the parents of the index cases we found nine maternal carriers and only one pater nal carrier. This presentation illustrates the need for individual ris k counselling of each carrier with reciprocal translocation regarding further family planning.