Regular ovulation is associated with regular menstruation. Some women have irregular periods, only occasional periods or even no periods and are therefore unlikely to be ovulating properly or at all. In this situation when a woman is trying to conceive, we can use medications to trigger normal follicle development and regular ovulation. For some women who do already have regular menstrual cycles, ovulation induction medication may be used to further maximise the potential of the ovulation.
Ovulation induction in more detail
Ovulation can be confirmed after the event by a blood test to measure for progesterone. We can be alerted to imminent ovulation by doing urine testing of luteinizing hormone (LH). This surge or spike of LH production, as it is known, occurs approximately 24 hours before ovulation so the most fertile period for conception is for 24 to 28 hours once the LH surge is detected.
For a few days prior to ovulation we can also, with ultrasound scanning, track the development of the “leading follicle”. This is the follicle which contains the egg which is likely to ovulate in a particular cycle. If a woman is having hormone treatment for fertility assistance, there may be several suitable follicles developing at the same time visible on ultrasound.
Problems with ovulation
There are many possible reasons why women may not ovulate regularly. Some women have a signalling problem between the brain and the ovaries which means that the normal hormone pathways do not flow properly. This results in irregular, rare or absent ovulation and menstrual cycles. This is common in women who exercise at a very high level, and in women who are underweight. It is also common in women who engage in shift work, for example flight attendants.
Some women have polycystic ovarian syndrome (PCOS), a very common hormonal condition associated with excess activity of some hormones and sometimes associated with weight gain, excess hair, acne and insulin resistance.
Various other hormonal imbalances may also cause irregular ovulation.
Very occasionally there may be a significant problem within the ovaries with the development of premature ovarian failure and damage to the little eggs and follicles. This can be temporary or permanent and is the only sort of ovulation problem which is not helped by the use of ovulation induction medications.
Ovulation Induction
There are various treatments to help women with irregular menstrual cycles to ovulate.
The most commonly used medicine is an oral preparation called clomiphene citrate. Clomiphene works by tricking the brain into thinking that it needs to send signals to the ovaries to help follicles and eggs develop. Another medication commonly used that is taken as an injection is called follicle stimulating hormone (FSH) and this works directly on the ovaries to develop follicles.
Both these medications may cause multiple follicle development. While we usually want to have multiple follicles develop when we use these hormones for IVF, this is NOT the case with ovulation induction. In Ovulation we really only want to stimulate development of a single egg, otherwise there is a risk of high-order multiple pregnancy resulting. For this reason we usually perform regular ultrasounds to assess the number and the rate of growth of these follicles.
Sometimes an additional medication called luteinizing hormone (LH) is also needed to help the oestrogen production in the ovaries and normal follicle development.
After the follicle has developed we may use another injection of recombinant hCG to actually trigger the egg to be released from the follicle.
The fertile time is for three days from the time of trigger or LH surge.
Clomiphene or FSH may be used in conjunction with timed intercourse, or even intrauterine insemination (IUI) (which ensures that the sperm is introduced into the uterus at the right time). We monitor cycles of ovulation induction by:
• vaginal ultrasound scans and/or urine tests to check follicle development
• a combination of urine and blood tests and urine tests to observe hormone levels.
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