Ovarian stimulation

Ovulation induction (OI) with controlled ovarian stimulation may be recommended for women who have normal tubes, and whose partners have a normal semen analysis, but who rarely or never ovulate. For women who do ovulate regularly, stimulation can also be used to maximise the potential of pregnancy by increasing the number of follicles that develop fully and, therefore, increasing the number of eggs that are ovulated during a cycle.

Two types of hormones may be used to stimulate ovulation:

  • Tablets of Letrozole®
  • Injections of follicle stimulating hormone (FSH) – Gonal-F®, Puregon® and Menopur®


Letrozole can potentially be a first choice treatment for stimulating ovulation for women under 30 years of age because of it’s low cost and ease of use. Normally Letrozole is a medication that is used for the treatment of breast cancer. It is an aromatase inhibitor and works by lowering the production of oestrogen.

When the enzyme aromatase is inhibited by Letrozole, oestrogen levels are suppressed. This results in the brain and pituitary gland increasing the output of FSH (follicle stimulating hormone).

In women with PCOS or anovulation (a problem with ovulation) the increase in FSH hormone encourages development of a mature follicle in the ovary and ovulation of an egg. This process is called ovulation induction.

Side effects can include hot flushes and headaches however the treatment duration for Letrozole is only five days so these should be short-lived. Other possible side effects include fatigue, nausea, constipation, diarrhea, joint pain.

As with any medication that stimulates the ovaries, there is an increased risk of multiple pregnancy. Studies have indicated that approximately 4% of the pregnancies conceived with Letrozole are twins.

Follicle stimulating hormone (FSH)

FSH is the hormone necessary for the development of the multiple follicles required for in vitro fertilisation (IVF).

FSH may also be used in smaller doses for ovulation induction or ovarian hyperstimulation in IVF. The FSH is made in the laboratory and is identical to human FSH. Because it is a protein that if taken orally would be digested in the stomach, FSH is given by injection under the skin, with a fine needle. There are three brands of FSH available in Australia – Gonal-F®, Puregon® and Menopur®. All are self-administered with pen-like devices (similar to those used for insulin by diabetics).

Using FSH to induce ovulation for getting pregnant naturally, as opposed to through IVF, can be tricky because of the risk of stimulating too many follicles and having a multiple pregnancy. This is why the body’s response is closely monitored with blood tests and ultrasounds.

When the lead follicle or follicles are the right size on ultrasound, ovulation is triggered with an injection of human chorionic gonadotrophin (hCG), which mimics the luteinising hormone (LH) surge.

Even with the most careful monitoring, more follicles can reach maturity than desired. Intercourse should be avoided because of the high risk of twins, triplets or an even higher-order multiple pregnancy. If this looks too likely, either the ovulation cycle that has been induced will need to be cancelled or a suggestion might be made to carry out an IVF procedure instead, in a separate treatment cycle.


Side effects from treatment with FSH include bloating and mood changes as estrogen levels rise. Some women experience a rash at the site of the injection. FSH treatment can occasionally cause a condition called Ovarian Hyperstimulation Syndrome (OHSS).

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