Detection of unbalanced chromosome segregations in preimplantation genetic diagnosis of translocations by short comparative genomic hibridization.

OBJECTIVE: To apply a comprehensive chromosomal screening through short comparative genomic hybridization (CGH) in the preimplantation genetic diagnosis (PGD) of translocations.
DESIGN: Clinical research study.
SETTING: A PGD laboratory and two IVF clinics. PATIENT(S): Three Robertsonian translocation carriers, two reciprocal translocation carriers, and a double-translocation carrier. INTERVENTION(S): After using the short-CGH approach in the reanalysis of two unbalanced embryos, discarded from a PGD for a reciprocal translocation carrier, the same method was applied in the PGD of day-3 embryos of translocation carriers. MAIN OUTCOME MEASURE(S): Ability of short CGH to detect partial chromosomal abnormalities in unbalanced embryos, translocation segregation proportions, and proportion of embryos carrying chromosomal abnormalities not related to the translocations. RESULT(S): The short-CGH technique detected errors resulting from the meiotic segregation of the chromosomes involved in the translocations and other abnormalities affecting the remaining chromosomes. Alternate segregation was detected most frequently among Robertsonian translocation cases, whereas unbalanced chromosome segregations were found predominantly in reciprocal ones. Aneuploidy and structural chromosome errors were found more frequently in Robertsonian than in reciprocal translocation carriers. Application of short-CGH PGD achieved pregnancy in two cases. CONCLUSION(S): Short CGH is a reliable approach for PGD of translocations, as it is capable of detecting partial chromosome errors caused by unbalanced segregations simultaneously to the screening of all chromosomes, and it may improve the results after PGD for translocation carriers.