Problems related to the laboratory part of treatment by in vitro fertilization and embryo transfer.

The successive stages leading to fertilization in mammals are reviewed in this article. Methods of human sperm preparation for IVF are described and the "ideal" delay between oocyte pick-up and insemination time is discussed, as well as methods to reduce the incidence of polyspermy. Different culture media and their supplementation are mentioned, as well as a semi-quantitative embryonic scoring system, defined by the IVF team of the Saint-Pierre Hospital in Brussels. Finally the optimal transfer time, and the handling of embryos at replacement are discussed.