The method proposed is based on a gradual fixation, and short-term hydration before softening and on a new technique of chromosome preparation. The latter is based on the sample softening in 60% acetic acid directly on the slide, its gentle shaking and spot-blotting, a careful spreading of the cell suspension on slide surface avoiding the usage of micropipets and other handlings causing metaphase plate breakage. The method provides a highly efficient karyotyping of human embryos within the 7-12th weeks of gestation.