Capacitated sperm, which swim at 1 to 3 mm/min are attracted to progesterone, which is secreted from the cumulus cells surrounding the oocyte. Progesterone binds to the CatSper receptor on the sperm membrane and increases intracellular calcium levels, causing hyperactive motility. The sperm will continue to swim towards higher concentrations of progesterone, effectively guiding it to the oocyte. Around 200 out of 200 million spermatozoa reach the ampulla.

Sperm preparation