Aromatase inhibitors (Femara, etc) can be used to treat infertility.
Some fertility experts are using letrozole (Femara) and other aromatase inhibitors off-label to induce ovulation.
Estrogen indirectly inhibits the release of gonadotropins. By blocking estrogen production, aromatase inhibitors increase gonadotropin release...leading to follicle stimulation and ovulation.
These drugs are sometimes tried in women who fail to conceive with clomiphene (Clomid, etc). Clomiphene is very effective at inducing ovulation, but actual pregnancies are low. It's thought that this is because of clomiphene's prolonged anti-estrogenic effects...due to a long half-life of 2 weeks. Clomiphene causes the cervical mucus to thicken and the endometrium to thin...possibly leading to implantation failure and early pregnancy loss.