Relationship of a human oocyte scoring system to oocyte maturity and fertilizing capacity.

A simple, quick, and semiquantitative human oocyte scoring system is described. Oocyte-corona-cumulus complexes were spread, either by tilting the dish or by aspiration of the fluid, and examined under the dissecting microscope. A maximum of four points was assigned to each of the following: cumulus expansion, cumulus appearance, amount of cumulus, corona expansion, corona appearance, and oocyte appearance. The oocyte score was significantly correlated to two important physiological parameters of oocytes, nuclear maturity (P less than .02) and fertilization rate (P less than .0001). This oocyte scoring system is useful for selecting oocytes for in vitro fertilization and embryo transfer (IVF-ET) or gamete intrafallopian tube transfer (GIFT), for training new laboratory personnel in recognizing the important characteristics of a mature oocyte, and in the standardized reporting of oocyte quality by different IVF-ET or GIFT programs.