Case report:
A 22-year-old healthy pregnant woman came to our laboratory for amniocentesis and fetal cytogenetic examination at 16 weeks of gestation. Invasive prenatal diagnosis was indicated because a balanced translocation involving chromosomes 9 and 20 was observed in her karyotype. She had suffered two consecutive early spontaneous abortions at that time. After the second miscarriage the couple underwent cytogenetic examination. The karyotypes were referred to us as 46,XY for the husband and 46,XX,t(9;20) for the wife.
During the third pregnancy ultrasound examination at 12 weeks of gestation was uneventful. Amniocytes were cultured for cytogenetic analysis and showed 46,XY,t(1;4;20;9)(q32;p13;p11.2;p13). After this result a second examination of the parental karyotypes was performed and showed that the mother carried the same complex chromosomal rearrangement.
Cytogenetic studies
Parental peripheral blood and amniocyte samples were obtained with informed consent and the karyotype analysis was performed using standard GTG and high-resolution banding.
Cytogenetic analysis on amniocytes revealed that the fetus had an apparently balanced complex chromosome translocation involving four chromosomes. Following the nomenclature for such a rearrangement (ISCN 1995) this translocation is: 46,XY,t(1;4;20;9)(1pter→1q32::9p13→9pter;4qter→4p13::1q32→1qter;20qter→20p11.2::4p13→4pter; 9qter→9p13::20p11.2→20pter) (fig. 1, 2).
Since this observation does not correspond to the reported rearrangement of maternal karyotype a second cytogenetic examination of the parents was performed. ?aternal karyotype revealed the same complex balanced chromosome rearrangement as the fetus. (fig. 3).

Fig.2 Partial karyotype of the fetus and schematic representation of the complex rearrangement of chromosomes 1, 4, 9 and 20.

Fig.3 The karyotype of the female translocation carrier - 46,XX,t(1;4;20;9)(1pter®1q32:: 9p13®9pter; 4qter®4p13::1q32 ®1qter; 20qter ®20p11.2::4p13 ®4pter; 9qter ® 9p13::20p11.2 ® 20pter).