Controlled Ovarian Stimulation is a process that involves hormonal regulation of the ovarian follicles to maximize retrieval during Ovum Pick Up in an IVF cycle. It is a process where patients are put on hormonal injections of Agonists or Antagonists, along with gonadotropins to artificially regulate and maximize multiple follicular growth to retrieve multiple eggs. This is stimulated compared to a single follicle growth and egg maturation in a natural cycle.