Step 1: Infertility in polycystic ovary syndrome (PCOS) is mainly due to anovulation. The goal of treatment is therefore to induce ovulation.
Step 2: Clomiphene citrate is a selective estrogen receptor modulator. It blocks estrogen receptors at the hypothalamus, removing negative feedback so that FSH and LH rise and stimulate follicular growth and ovulation.
Step 3: Because it is oral, inexpensive and effective, clomiphene citrate is the first line agent for ovulation induction in an anovulatory PCOS woman, usually after lifestyle and weight measures.
Step 4: Injectable gonadotropins (FSH), GnRH and assisted reproductive techniques such as IVF are reserved for women who fail to ovulate or conceive on first line therapy. Hence the answer is clomiphene.