Laser scanning confocal imaging of abnormal or arrested human preimplantation embryos.

Purpose: The improved resolution and optical sectioning of a confocal microscope make it an ideal instrument for extracting three-dimensional information, especially from extended biological specimens such as human embryos. The staining of actin together with chromatin allowed us to specify the architecture of the embryo and the appearance of the nucleus.

Methods: F-Actin and chromatin distributions were visualized using laser scanning confocal microscopy in "fresh" and "cryopreserved" human preimplantation embryos obtained by in vitro fertilization.

Results: The current study revealed a high rate of multinucleation in arrested or poor-quality embryos (89%, in grade IV embryos).

Conclusions: Confocal microscopy revealed high levels of multinucleated blastomeres, suggesting that the probable cause of arrested development in these embryos was due to multinucleation of blastomeres.