Sex Diagnosis and Sex Chromosomal Mosaicism in Normal Human Preimplantation Embryos

Abstract

The sex of human preimplantation embryos was determined by fluorescent in-situ hybridization (FISH), and the reliability of this method was evaluated. Preimplantation sex determination by FISH was performed with blastomeres dissociated from pre- implantation embryos with 2 pronuclei in the 2-8 cell stage that were obtained by intracytoplasmic sperm injection (ICSI). Dual color FISH analysis was performed with DXZ1 and DYZ1, X and Y chromosome-specific probes, respectively. The detection sensitivity of DXZ1 and DYZ1 was evaluated with interphase nuclei of human lymphocytes obtained from normal males and females. The signal detection rate in these nuclei was 92.0% (460/500) in the males and 89.4% (447/500) in the females. The fixation rate of single blastomeres determined by FISH was 88.7% (86/97). The sex determined by FISH was the same in all blastomeres within the embryo in 20 (80%) of 25 embryos; 11 embryos were determined to be males and 9 to be females. The other 5 embryos (20%) showed sex chromosomal mosaicism. When the results in 2 blastomeres are normal and consistent, the probability that the remaining part of the embryo was mosaic was 12% (3/25). When the sex of the entire embryo is determined by biopsy of 2 blastomeres instead of 1 blastomere, mosaicism can therefore be excluded with a reliability of 88%, and more accurate diagnosis is possible.