Letrozole is a medication that prevents the production of estrogen by a woman’s ovaries which causes the pituitary gland to release to more Follicle Stimulating Hormone (FSH). FSH is the main hormone that allows eggs (oocytes) within the ovary to mature. Letrozole is a prescription medication that is started on day 3 or day 5 after your menstrual cycle begins and taken for a total of 5 days (cycle day 3 to 7 or cycle day 5 to 9). The usual starting dose is 2.5 mg (1 pill) or 5 mg (2 pills) daily and women usually ovulate 5-12 days after the last dose. After your doctor has prescribed Letrozole, you should contact your doctor’s office on day 1 or 2 of your cycle so that an ultrasound can be performed prior to starting your medication. The ultrasound is used to confirm there are no ovarian cysts (follicles which did not release an egg during a previous cycle) that may interfere with your treatment. After your treatment cycle has begun, your doctor will follow the maturation of the eggs an ultrasound. The ultrasound is used to measure the growth and number of follicles (fluid-filled compartments containing the eggs) within the ovary. When the follicles are large enough, it indicates to your doctor that the eggs (oocytes) inside are mature and it is time to consider intercourse or insemination. An injectable medication such as Ovidrel or Novarel will often be prescribed to the patient to cause ovulation prior to intercourse or insemination. Common symptoms experienced with Letrozole include hot flushes, night sweats, headaches, nausea, fatigue, weight gain and joint or muscle pain or stiffness. Twin & triplet pregnancy rates are comparable to clomiphene.