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Letrozole, or Femara, is a pill that can be taken to improve fertility

Letrozole works by decreasing estrogen (female hormone) levels in a woman’s body. When this happens, the brain and pituitary sense that there is not enough estrogen around. As a result, the pituitary releases more FSH, which signals the ovary to cause eggs to start developing.

Like clomiphene (Clomid), letrozole (Femara) may cause one or more follicles, and therefore eggs, to develop, although it does not tend cause multiple follicle development as often as Clomid. Drs. Munch and Han tend to use this medication in a few specific situations.

  • When Clomid fails to cause ovulation, letrozole may induce ovulation because it works in a different way to increase FSH production from the brain.
  • When Clomid causes a thin uterine lining, this medication can cause ovulation without having this negative side effect.
  • For women who have used Clomid unsuccessfully, but are not yet ready or able to move on to injectable gonadotropins, we may try this drug.
  • We may try this medication when there is an over-response to Clomid (too many eggs for ovulation).

This medication was actually developed as a treatment for breast cancer, since it keeps estrogen levels low for patients at risk of breast cancer recurrence. While it is not a chemotherapeutic drug (and will therefore not cause side effects like hair loss, nausea/vomiting, etc.), it is the lowering of estrogen production that also makes it useful for ovulation induction.

Side effects of letrozole

Letrozole usually does not cause as many side effects as Clomid. However, nausea, fatigue and headaches can occur, and in rare cases, some women also report hot flashes.


If taken during pregnancy, letrozole can cause birth defects. However, when taken to cause ovulation, this drug appears to be safe. It is metabolized before pregnancy occurs, and contemporary studies have shown no increased risk of birth defects in a pregnancy resulting from ovulation induction with this medication. It is a safe and commonly used medication to help with ovulation induction for women with polycystic ovary syndrome (PCOS), as well as other infertility conditions.

If you would like to learn more about how we can help you achieve pregnancy, please contact our San Antonio fertility center to schedule an appointment with Dr. Erika Munch or Dr. Eric Han.

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