Ovulation induction: medicines to help you ovulate

What ovulation induction is

To get pregnant, an ovary needs to release an egg each cycle. This is called ovulation. Some people ovulate rarely or not at all, which often shows up as irregular or absent periods.

Ovulation induction means using medicines to help the ovaries develop and release an egg. It is usually combined with timed sex, and sometimes with IUI (intrauterine insemination).

It is different from IVF. The aim is to grow one, or at most a few, eggs that are released naturally, not to collect many eggs in a procedure.

Who it tends to suit

Ovulation induction is mainly for people whose difficulty is with ovulation, while the fallopian tubes are open and sperm results are within the usual range or close to it. Common situations include:

• PCOS (polycystic ovary syndrome). This is the most common cause of irregular ovulation.
• Irregular cycles without a clear cause.
• Some hormone conditions, such as problems with the hormone signals from the brain. These may need a different, specialist approach.

Before starting, doctors usually check the thyroid, prolactin and other hormones, look at the tubes, and arrange a semen analysis for the male partner. Treating ovulation alone will not help if there is another cause.

Tablets

The two tablets most often used are:

• Letrozole. It lowers oestrogen levels for a short time, which prompts the brain to release more of the hormone that grows follicles. The 2023 international PCOS guideline recommends letrozole as the first-choice medicine for helping ovulation in PCOS.
• Clomifene (clomiphene). It works in a similar way by blocking oestrogen signals in the brain. It has been used for many decades.

Tablets are usually taken for a few days early in the cycle. Your doctor will decide which medicine and dose suits you. Do not take these medicines without a doctor's supervision.

Possible side effects include hot flushes, headaches, bloating, mood changes and, rarely, visual disturbances. Report any changes in your vision to your doctor.

Injections

If tablets do not lead to ovulation, or ovulation happens but pregnancy does not follow after several cycles, doctors may suggest gonadotrophin injections. These contain the hormones that directly stimulate the ovaries.

Injections are more powerful than tablets, so they need closer monitoring. They are given at low doses in ovulation induction, very differently from IVF.

Monitoring with scans

Your clinic may track your cycle with ultrasound scans, usually done through the vagina. These show how many follicles (small fluid-filled sacs that each hold an egg) are growing and how large they are. Blood tests may also check hormone levels or confirm ovulation.

Monitoring helps the doctor:

• confirm that the medicine is working
• time sex or IUI
• spot when too many follicles are growing

Caution. If several follicles grow at once, there is a higher chance of twins or more. Multiple pregnancy carries higher risks for both the pregnant person and the babies. If too many follicles develop, your doctor may advise not having sex that cycle or may cancel it. This can be disappointing, but it is a safety step.

Injections also carry a small risk of ovarian hyperstimulation syndrome (OHSS), where the ovaries over-respond. This is less common with ovulation induction than with IVF.

How long it is usually tried

Doctors usually try ovulation induction for a limited number of cycles and then review the plan. If ovulation is happening but pregnancy has not followed, they may suggest further tests or a different treatment. Ask your doctor at the start how many cycles they suggest before reviewing.

Good to know. For people with PCOS who have a higher weight, small changes in activity and diet can sometimes help ovulation. This is not about blame, and treatment does not have to wait for weight loss if your doctor feels it is appropriate.

When to see a doctor

See a doctor if your periods are irregular, very infrequent or absent, or if you have been trying for 12 months (6 months from age 35) without a pregnancy. If you are on ovulation medicines, contact your clinic promptly if you have tummy pain, bloating that is getting worse, or changes in your vision. Call 112 or go to the nearest hospital if you have severe tummy pain, breathlessness or fainting. You can book an online consultation to talk through irregular cycles.