OBJECTIVETo perform spectral karyotyping (SKY), fluorescence in situ hybridization (FISH) and conventional karyotyping on prenatally detected marker chromosomes and complex chromosomal aberrations.

METHODSFive marker chromosomes and 2 complex chromosome aberrations diagnosed by G banding were collected. SKY was performed to verify the composition of marker chromosomes. FISH was used to confirm the diagnosis when necessary. In certain cases, C or N banding technique was employed to verify the composition of chromosomes. Results of ultrasonography and pregnancy outcome were reviewed.

RESULTSAmong the 5 marker chromosomes, 2 were large and 3 were medium in size, 4 were de novo and one was inherited from the father. By SKY analysis, 2 marker chromosomes have originated from non-acrocentric chromosomes (4 and 9), whilst the other two have originated from acrocentric chromosomes (21 and 22). The remainder was derived from X chromosome. The SKY results were confirmed by FISH in 3 cases. Four cases have chosen to terminate the pregnancy after genetic counseling. A fetus with inherited paternal marker chromosome was delivered at term, and showed normal development during the first year of life. As for the other 2 cases with complex chromosome aberrations, by SKY examination, one had duplication in chromosome 8 and the other had chromosome rearrangements derived from translocation between chromosomes 2 and 6. In the latter case the fetus was delivered at term but showed developmental retardation at 6 months.

CONCLUSIONSKY in combination with FISH can facilitate identification of the origins of marker chromosomes as well as complex chromosomal aberrations. With combined information from ultrasonography, SKY and FISH, effective counseling may be offered to the patients.