Influence of mosaicism on sexing of human preembryos detected by the polymerase chain reaction.

PURPOSE: Preimplantation sex determination using a single cell by the polymerase chain reaction (PCR) was investigated to elucidate the influence of mosaicism.

METHODS

The SRY and ZFX genes were coamplified as target sequences for the Y and X chromosomes, respectively. The sensitivity of the single and nested PCR method was examined initially followed by amplification of single amniocytes by the nested PCR. Then the sex of single blastomeres at the three- and nine-cell stages was determined by the nested PCR.

RESULTS

The nested PCR was 10(4)-fold more sensitive than the single PCR. Sex determination was possible in 97.5% (117/120) of the blastomeres tested. However, the correspondence rate for all blastomeres within a single embryo was only 60% (12/20 embryos). Among the remaining embryos for which sexing of all blastomeres was not consistent, only one blastomere showed findings indicating the presence of mosaicism (or pseudomosaicism).

CONCLUSIONS

At least two blastomeres need to be assessed when determining the sex of an embryo in order to avoid misdiagnosis due to mosaicism (or pseudomosaicism).