First births after preimplantation genetic diagnosis of structural chromosome abnormalities using comparative genomic hybridization and microarray analysis.

BACKGROUND

Balanced chromosomal rearrangements represent one of the most frequent indications for preimplantation genetic diagnosis (PGD). Although fluorescence in situ hybridization (FISH) has been successfully employed for diagnosis in such cases, this approach usually restricts assessment of the chromosomes involved in the rearrangement. Furthermore, with FISH-based strategies, it is sometimes necessary to create patient-specific protocols, increasing the waiting time and costs. In the current study, we explored the use of two comprehensive chromosome screening methods, conventional metaphase comparative genomic hybridization (CGH) and microarray-CGH (aCGH), as alternatives for PGD of chromosome rearrangements.

METHODS

The study included 16 patients who underwent 20 cycles of PGD for a variety of chromosome rearrangements (reciprocal or Robertsonian translocations or inversions). Testing was performed at various embryonic stages using CGH (9 cases) or aCGH (11 cases).

RESULTS

Results were obtained for 121 out of 132 samples (91.7%). Of the diagnosed samples, 48.8% were found to carry abnormalities associated with the rearrangement, either alone or in combination with other chromosomal abnormalities. A further 28.9% of samples were normal/balanced for the rearranged chromosomes, but affected by aneuploidy for other chromosomes. Only 22.3% of samples were chromosomally normal. Of the 15 patients who completed their treatment cycles, 5 became pregnant after one or two cycles resulting in four healthy births. The delivery rate per cycle was 21% (27% per embryo transfer).

CONCLUSIONS

This is the first study to describe the clinical application of comprehensive chromosome screening applied to polar bodies, blastomeres or trophectoderm cells from patients carrying inversions and translocations. Using these techniques, most patients requesting PGD for a chromosome rearrangement can be treated using a single protocol. Additionally, the detection of abnormalities affecting chromosomes unrelated to the rearrangement may assist in the selection of viable embryos for transfer.