Carriers of balanced complex chromosome translocations (BCT) are observed very rarely among humans. The majority of such cases occurs de novo and associate with congenital abnormalities, mental retardation and reproductive problems.

We report a case of a 4-way apparently balanced reciprocal translocation involving chromosomes 1, 4, 9 and 20 identified during prenatal diagnosis. The karyotype of cultured amniocites was determined as 46,XY,t(1;4;20;9)(q32;p13;p11.2;p13). Later the same chromosome rearrangement was detected in the mother of the fetus.

So far only a small number of cases with segregation of complex chromosome rearrangement in a balanced form trough two or more generations have been reported. To our knowledge this is the second report of familial balanced 4-way translocation ascertained during prenatal diagnosis.