Mosaicism for a balanced reciprocal translocation is uncommon. These two new cases were
detected during investigation of infertility and miscarriages. Otherwise, the probands were
normal. Of five previously described cases, only one was possibly syndromal. More reports
of this class of chromosomal aberration are needed to assess accurately the risk of
phenotypic abnormalities.

We describe 2 cases of balanced reciprocal translocation (BRT) mosaicism. The frequency
of this aberration in the population referred to our laboratory was determined and compared
to those frequencies reported in the literature by other clinical cytogenetics laboratories. The
extent of BRT mosaicism was also examined in surveys of prenatal populations, which are
less likely to have a bias due to ascertainment on the basis of abnormal phenotype. The
frequencies in the postnatal and prenatal populations examined in this study were …