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Ovulation induction using Letrozole

Date issued: July 2021

Review date: July 2023

Ref: A-471

PDF:  Ovulation inducition using Letrozole final July 2021.pdf [pdf] 385KB

What is Letrozole?

Letrozole belongs to a class of drugs called aromatase inhibitors. The prime and only licensed use of Letrozole is as an additional (adjuvant) treatment of breast cancer in post-menopausal women. It is, however, being increasingly used as a treatment by fertility specialists to aid the development of ovarian follicles. It may be recommended by your doctor as an alternative to Clomiphene or Tomixifen if you have polycystic ovarian syndrome (PCOS) and have not responded to clomiphene or Tomoxifen.

What are the advantages of taking Letrozole?

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, something seen with Clomiphene, resulting in higher birth rates than with standard treatment. Letrozole is also associated with more cycles where only one follicle develops and hence lowers multiple pregnancy rates compared with clomiphene (3.4% v 7.4% respectively).

Are there any risks with Letrozole? 

The risk of congenital abnormalities in babies appears to be lower than with Clomiphene and is comparable with babies conceived naturally. 

Are there any side effects? 

The most common side effect of taking Letrozole is hot flushes, as well as occasional fatigue and dizziness. Treatment with Letrozole is off-licence as the drug company has not applied for a specific licence to allow treatment for fertility and is therefore not approved for ovulation induction.

How effective is Letrozole?

Most women will ovulate over six months of treatment; Letrozole can be taken for 12 months.  The success rate is approximately 25 - 30 percent.

What is the treatment process?

Day ONE of menstrual cycle: contact the fertility nurse on 01752 430089 to arrange a scan. Please leave a message if the nurse is not available.

Day TWO of the cycle: start Letrozole as advised by the fertility team; take one tablet every day for five days.

If you have irregular cycles, you may be prescribed Provera/Northisterone which can help induce a bleed. You will need to take a pregnancy test before taking Provera/Northisterone.

Monitoring after first cycle of Letrozole

You will need a scan at day 10-12 after starting the medication to look for a dominant follicle. The follicle should be around 15mm on day 10-12. We are looking to see that there is ONE dominant follicle. If we find there is more than one then you must use condoms otherwise there is a risk of a multiple pregnancy.  Occasionally there can be several follicles with one that appears more dominant, in this situation you will be advised to have a further scan after 2-3 days.  

What happens if I do not conceive?

If the scans and blood tests show that you have responded well and ovulated in your first cycle, continue to take Letrozole in your next menstrual cycle. Please contact the fertility nurse for a further prescription of Letrozole on email s.black4@nhs.net  You should not need further monitored scans. If you have not conceived after 6 months of treatment then you will be referred back you your consultant.

What to do if I have not responded to Letrozole?

If the scans show that your ovaries have over-stimulated, the dose of Letrozole may be reduced in your next cycle. You will be advised to have protected intercourse (with condoms) to avoid the risk of a multiple pregnancy. Please let the fertility team know if you feel unwell.

What to do if I have a positive pregnancy test?

If you have a positive pregnancy test, please inform your fertility nurse, Sarah Black s.black4@nhs.net Sarah will book you an EPU scan at 8 weeks, in the Early Pregnancy Unit, Lancaster Suite Level 6. You will also need to book in with your community midwife who will organise a dating scan which is usually at around 12 weeks. Your community midwife can be accessed through your GP. Your fertility nurse will be able to guide you if there is a need for you to have an ultrasound scan performed early; this may be because you have previously had an ectopic or a molar pregnancy, previous surgery on your fallopian tubes or if you have certain health conditions such as diabetes or being high risk for blood clots. 

If you experience any of the following, you should contact your GP for a referral to EPU (Early Pregnancy Unit) Lancaster suite level 6

  • Lower abdominal or pelvic pain

  • Vaginal bleeding

Patient advice and Liaison Service (PALS)

If you have a compliment, complaint or concern please contact our PALS team on (01752) 439884

Email: plh-tr.PALS@nhs.net

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