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How many cycles of letrozole are needed to get pregnant?

Medically reviewed by Sally Chao, MD. Last updated on July 20, 2023.

Official answer

by Drugs.com

There is no set number of cycles of letrozole when treating female infertility. How many cycles to try is a decision made between you and your provider. It may be influenced by drug cost, availability of health insurance and side effects experienced.

There is no consensus on the maximum number of cycles of letrozole to try before moving on to an alternative therapy. One study that looked at using letrozole to stimulate ovulation in those with polycystic ovary syndrome limited study participants to 5 cycles of the drug. The average time to become pregnant in the group taking letrozole was 90 days, or about 3 cycles. About 28% of women taking letrozole resulted in a live birth in the study.

Letrozole is a drug in the class of medications called aromatase inhibitors. It is approved by the U.S. Food and Drug Administration (FDA) for the treatment of certain types of breast cancer. It is used off-label to treat female infertility. Off-label use is when a provider prescribes a medication that has been studied and found to be safe and effective for one purpose for a different purpose.

Letrozole is used to stimulate ovulation. It does this by affecting certain female hormone levels. Letrozole is a tablet and is taken orally daily for 5 days starting between days two and five of menses. The usual initial dose is 2.5 mg. You are then monitored to determine when you’re ovulating and encouraged to have intercourse around that time. If pregnancy does not occur with the first cycle, the process may be repeated for the next cycle, and the letrozole dose may be increased by 2.5 mg increments (up to 7.5 mg).

Infertility is defined as difficulty getting pregnant after 1 year of regular unprotected sexual intercourse. The most common cause of female infertility is problems with ovulation (irregular or none), but it can also be caused by advancing age, lifestyle or other health conditions. Determining the cause for infertility requires an extensive evaluation. Possible treatments depend on the cause of the infertility and include lifestyle changes, surgery or medications.

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References
  1. Legro RS, Brzyski RG, Diamond MP, et al. Letrozole versus clomiphene for infertility in the polycystic ovary syndrome. N Engl J Med. 2014;371(2):119-129. https://doi.org/10.1056/nejmoa1313517.
  2. U.S. Food and Drug Administration (FDA). Femara. April 2018. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/020726s035lbl.pdf. [Accessed July 15, 2021].
  3. American Society for Reproductive Medicine (ASRM). Medicines for Inducing Ovulation. 2016. Available at: https://www.reproductivefacts.org/news-and-publications/patient-fact-sheets-and-booklets/documents/fact-sheets-and-info-booklets/medications-for-inducing-ovulation-booklet/. [Accessed July 19, 2021].
  4. U.S. Food and Drug Administration (FDA). Understanding Unapproved Use of Approved Drug "Off Label." February 5, 2018. Available at: :https://www.fda.gov/patients/learn-about-expanded-access-and-other-treatment-options/understanding-unapproved-use-approved-drugs-label. [Accessed July 19, 2021].
  5. American College of Obstetrics and Gynecology (ACOG). Fertility FAQs. Available at: https://www.acog.org/womens-health/faqs/treating-infertility. [Accessed July 19, 2021].

Read next

Letrozole is not chemotherapy, it is a type of hormone therapy that is used to treat people with breast cancer that is hormone receptor-positive. If your cancer is hormone receptor-negative, then letrozole will not be of any benefit. Traditional chemotherapy agents stop cancer cells from growing, dividing, and making more cells. Letrozole works by blocking the action of the enzyme aromatase, which prevents the body from converting androgens into estrogens. Estrogen is a hormone that causes estrogen receptor-positive (ER+) breast cancer to grow. Letrozole belongs to the class of medicines known as aromatase inhibitors. Continue reading

Although diabetes and blood sugar increases are not listed as a side effect of letrozole treatment, treatment with letrozole is associated with a significantly increased risk for high blood sugar levels and diabetes. An Israeli study that investigated 2,246 breast cancer survivors found that women treated with letrozole were 4.3 times more likely to develop diabetes than women not taking letrozole, although the number of women prescribed letrozole was small. Overall, women prescribed any sort of hormone treatment (either tamoxifen or an aromatase inhibitor such as letrozole) had a 2.5 times higher risk of diabetes. Continue reading

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