An improved technique for molecular cytogenetic analysis of human preimplantation embryos with fluorescence in situ hybridization.

OBJECTIVE : To develop a method for the cytogenetic evaluation of preimplantation embryos using nonradioactive centromeric probes for chromosomes 1, 16 and X. STUDY DESIGN : The embryos used for this study were either fragmented or polyploid embryos rejected from an in vitro fertilization program. Prior to in situ hybridization, the embryos were treated with 0.5% protease. After application of gradual fixation, conventional hybridization protocol was followed. RESULTS : Ten of 11 embryos showed hybridization signals suggesting that the success rate of in situ hybridization of human embryos is improved when a modified method of digesting the zona pellucida and gradual fixation with removal of the cytoplasm are used. CONCLUSION : The method described in this study demonstrates that the zona pellucida is the key to successful in situ hybridization of whole human embryos. Wren the zona pellucida is removed, penetration by a probe becomes possible. (J