Novel technologies for selecting the best sperm for in vitro fertilization and intracytoplasmic sperm injection.

The increasing focus on developing new tools to more accurately diagnose and select individual sperm before intracytoplasmic sperm injection will allow us to counsel and treat couples with greater confidence and efficiency. Current sperm selection techniques are based on the premise that if an ejaculated spermatozoon has cleared spermatogenesis with the correct morphology and/or membrane properties then it is most likely normal. Techniques that are designed to prepare a clean "normal" sperm population or that assist in selecting an individual "normal" spermatozoon are currently being investigated. The use of techniques, including density-gradient preparation, electrophoretic separation, microfluidics, high-magnification sperm morphology selection, and hyaluronic acid binding, is discussed. The research evidence that supports the interrelated developmental and genetic integrity of the selected sperm, particularly sperm DNA damage and clinical outcome evidence are presented.