Unexpected inherited chromosomal translocation during prenatal diagnosis for maternal age: Risk for a nondetectable karyotype imbalance in offspring

An unexpected t(1;19) translocation is described in a fetus. Inherited from the mother, this translocation was found during the course of a normal pre natal diagnosis made for maternal age. The very short length of chromosomal translocated segments and their labelling pattern made high-resolution cyt ogenetic methods and fluorescence in situ hybridization techniques necessar y for the correct identification of this karyotype rearrangement, both in m other and fetus. Different modes of meiotic segregation, leading to potenti al erroneous prenatal diagnoses, are discussed.