Follicular fluid meiosis-activating sterol (FF-MAS) is an intermediate in cholesterol biosynthesis from lanosterol that is found at high concentrations in mammalian ovarian follicular fluid. It increases survival of human oocytes isolated from patients with polycystic ovarian syndrome (PCOS) and improves cytoplasmic maturation of immature rodent and porcine oocytes in vitro. FF-MAS promotes completion of meiotic maturation to metaphase II and increases the rate of successful in vitro fertilization (IVF) in isolated mouse oocytes. Formulations containing FF-MAS have been used to improve embryo quality and implantation rate during IVF.