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Aim of treatment
Letrozole is now recommended as the first line treatment for induction ovulation.1 The prime and only licensed use of letrozole is an additional (adjuvant) treatment of breast cancer in post-menopausal women. It is not licensed for ovulation induction; however, it is being increasingly used as a treatment by fertility specialists to aid the development of ovarian follicles. A verbal consent is taken from all patients before the treatment is commenced.
The aim of treatment is to produce a single dominant follicle and restore natural ovulation to give you a normal chance of conception. Many studies have recently shown that using letrozole for ovulation induction results in better rates of successful ovulation and has no adverse effects on the lining of the womb sometimes seen with clomiphene citrate. This results in 40-60% higher birth rates with letrozole compared to clomiphene.
What does it involve?
The treatment involves the use of a tablet called letrozole to stimulate the growth of the follicles (fluid filled cysts in which eggs mature) and the production of a mature egg.
What will I need to do?
- Take letrozole once a day on days 2-6 of the menstrual cycle to stimulate the ovaries to produce eggs.
- Have intercourse around the time of ovulation when you are most fertile.
- Have a blood test (for progesterone) around day 21 of the cycle to confirm that you ovulated.
Am I suitable for this treatment?
You are suitable to have the treatment if:
- You are not ovulating regularly
- Your partner has a satisfactory sperm count
- You are expected to have, or are proven to have, at least one patent fallopian tube.
- You have achieved optimum control of your medical conditions, optimal weight (ideally BMI< 30) and take Folic acid and Vitamin D.
What are the risks associated with ovulation induction with letrozole?
- Multiple pregnancy. 3.4% of etrozole induced pregnancies are twins. This is because more than one egg may develop. Triplets are extremely rare. The rate is significantly lower than induction of ovulation with clomiphene citrate, where it was estimated to be 5-7%. For this reason, we do not offer ‘follicle tracking’ with ultrasound scans when taking letrozole.
- Ovarian Hyperstimulation. Very rarely, patients may over-respond to letrozole and produce too many follicles. This can cause abdominal discomfort, bloating and nausea. The condition will be confirmed on ultrasound scan, where too many follicles would be seen to be growing. You would be advised NOT to get pregnant until your next period starts.
- Hot flushes
- Fatigue and dizziness
- Headaches, muscle aches, blurred vision
If you experience problems with vision, pain or swelling in the abdomen or vomiting, please stop taking the medication and seek advice from your Fertility Consultant.
What are the success rates?
The cumulative ovulation rate with letrozole for up to five cycles is 61.7%, which is higher than with clomiphene citrate (48.3%). Women who received letrozole had more cumulative live births than those who received clomiphene citrate (27.5% vs.19.1%).
How do I start?
You will be advised to start letrozole at the dose discussed with your gynaecologist, usually one 2.5 mg tablet . It is taken once a day for five days, starting on the second day of your cycle (days 2-6). You will need a blood test for progesterone on day 21 of your cycle to confirm ovulation. You need to call the fertility nurse at FPH or WPH for the result (see page 6 for contact details).
What is the next step?
If your blood test confirms ovulation, your period is due 7-10 days after the blood test. If your period does not come, you will be asked to perform a pregnancy test at home and phone the fertility nurse (FPH) or fertility secretary (WPH) with the results (see page 6 for contact details). They will arrange the appropriate date for the next scan.
If your period comes, start the same dose of letrozole from day 2-6 of your period and continue for the next 3-5 cycles, but you will not need blood tests.
Approximately 30% of patients do not respond to the initial letrozole dose. If this happens, you will be asked to restart the treatment on a higher dose of letrozole, and a further prescription will be given if necessary. You may need a medication called medroxyprogesterone acetate to cause a bleed so the next treatment cycle can be started.
If you do not get pregnant after 3-6 cycles or do not ovulate despite increasing the dose of letrozole, we will arrange a follow up appointment to discuss what to do next.
Contact information
Fertility nurse (Frimley Park Hospital) and (Wexham Park Hospital) - 07769936082
Contact us
If you have any queries relating to this information, please contact the Gynaecology service.
About this information
Service:
Gynaecology
Reference:
L/106
Approval date:
11 May 2026
Review date:
1 May 2029
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Important note
This page provides general information only. It is developed by clinical staff and is reviewed regularly every 3 years for accuracy. For personal advice about your health, or if you have any concerns, please speak to your doctor.