Ovarian hyperstimulation (also called controlled ovarian hyperstimulation) is where a regimen of fertility medications are used to stimulate the development of multiple follicles of the ovaries in one single cycle, resulting in superovulation (release of a larger-than-normal number of eggs). It may be used as a part of in vitro fertilization. Treatment cycles are typically started on the third day of menstruation. In contrast, when referring to the reversal of oligoovulation or anovulation, the preferred term is rather ovulation induction.