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[Study on the mechanism of oocyte aneuploidy formation by multicolor fluorescence in situ hybridization].

OBJECTIVE
To investigate the mechanism of oocyte aneuploidy formation.


METHODS
The unfertilized oocytes were fixed 1-3 days after oocyte retrieval. Multicolor fluorescence in situ hybridization (M-FISH) was performed according to the Vysis protocol to check the chromosome status in oocytes by using centromeric enumerator probes for chromosomes 16, 18 and locus-specific probes for chromosomes 13, 21 and 22.


RESULTS
47% oocytes were found to be normal, while 53 % oocytes were abnormal. Nondisjunction was found in 22(18%) oocytes, unbalanced predivision of chromatids in 15(12%) oocytes, balanced predivision of chromatids in 45(36%) oocytes. The balanced predivision rate in oocytes aged in vitro>24h was much higher than that in oocytes aged in vitro<or=24h (P<0.01).


CONCLUSION
Both nondisjunction, balanced and unbalanced predivision of chromatids are involved in the oocyte aneuploidy formation. Balanced predivision is related to the time in culture.