Background: The slow-freezing method is one of the most popular techniques to freeze human oocytes and it is also used in routine in vitro-fertilization (IVF) programs, particularly in those countries where embryo freezing is not allowed. Slow-freezing damages some of the structures of the egg, among which the meiotic spindle (MS) and the zona pellucida (ZP). Polarized Light Microscopy (PLM) pe...