Ovulation Induction, known as ovarian stimulation:, entails using injectable fertility drugs such as Follistim, Gonal-F, Menopur, Repronex in order to stimulate the ovary to produce several oocytes. A natural, unstimulated cycle usually results in one mature oocyte and is unlikely to result in a pregnancy in IVF. A larger number of oocytes improves the odds of pregnancy, although it also increases the likelihood of multiple births.