The analysis of meiotic segregation patterns and aneuploidy in the spermatozoa of father and son with translocation t(4;5)(p15.1;p12) and the prediction of the individual probability rate for unbalanced progeny at birth.

Reciprocal chromosomal translocations (RCT) have long been recognized as important etiological factors in reproductive failure. In the present study, the meiotic segregation patterns of the spermatozoa of two related t(4;5)(p15.1;p12) carriers (proband and his father) were compared to the empirical data from a three-generation pedigree for risk assessment. Cytogenetic analysis of the metaphase chromosomes was performed, and triple color fluorescence in situ hybridization (FISH) was applied to the sperm heads. Similar patterns of meiotic segregation were observed for both carriers, despite the finding of teratozoospermia in the proband but not in his father. In addition, an increase of aneuploidy in chromosome 15 in the proband and aneuploidy of chromosomes X and Y in the father were observed. The high rate of miscarriages (6/10 pregnancies and 4/7 pregnancies after ascertainment correction) in this family could be explained by the genetically unbalanced karyotype and fertilization mediated by the unbalanced spermatozoa observed for both men at a frequency of more than 60%. The risk assessment for unfavorable pregnancy outcomes was predicted as 1.6% for unbalanced progeny at birth and about 30% for miscarriage. These figures may be used as guidelines for the genetic counseling of families with similar RCT.