CYCLE MONITORING

Ovulation induction is a procedure that enhances ovulation, with the aim of increasing the number of eggs released per cycle and maximising the chances of conception. In cases of an irregular menstrual cycle or known anovulation, we use medications that induce ovulation, such as clomiphene citrate or, alternatively, letrozole (FEMARA).

Indications

Women with anovulation (with regular transvaginal ultrasound monitoring)

Mild ovarian stimulation in women with a low response to conventional stimulation (poor responders)

Age under 35

Cases where conventional ovarian stimulation is not permitted for medical reasons

Women with a history of breast cancer (letrozole / Femara)

The procedure is monitored with regular transvaginal ultrasound scans and blood hormone tests, so that the effect of the hormonal medication can be assessed and the dosage tailored to the findings of each test.

Clomiphene citrate: Clomiphene citrate binds to oestrogen receptors in the brain, sending it a false signal that oestrogen is lacking. This signal prompts the brain, via the pituitary gland, to produce larger amounts of endogenous gonadotrophins (FSH, LH) than in a natural cycle, and these in turn stimulate the ovaries to produce more than one follicle.

It is usually given from day 3 to day 7 of the cycle at a dose of 100mg a day, increased to 150mg if the ovarian response is not satisfactory. Follicles are considered mature when their mean diameter exceeds 18mm, at which point the hormone human chorionic gonadotrophin (hCG) is given to trigger final follicular maturation, which leads to spontaneous ovulation 32-36 hours later. If pregnancy has not been achieved after 4-6 treatment cycles, more potent medications such as gonadotrophins are used.

The advantages of this treatment are its low cost and ease of use. Its disadvantages include a low pregnancy rate of 8-15% per cycle, the possibility of a twin or ectopic pregnancy, the possibility of ovarian hyperstimulation, failure of the medication, and all its side effects, such as vasomotor symptoms and changes in the consistency of the cervical mucus.

Letrozole (FEMARA): Letrozole selectively inhibits the enzyme aromatase and sharply reduces oestrogen production by the body's tissues. Its main indication is as adjuvant treatment for women who have had surgery for breast cancer, to protect them from the hormones their body produces.

Their ability to suppress oestrogen production is also used in infertility to induce ovulation. Low oestrogen levels force the pituitary gland to produce larger amounts of endogenous gonadotrophins (FSH, LH) than in a natural cycle, and these in turn stimulate the ovaries to produce more than one follicle.

It is usually given from day 3 to day 7 of the cycle at a dose of 4mg a day, increased to 6mg if the ovarian response is not satisfactory. Follicles are considered mature when their mean diameter exceeds 18 mm, at which point the hormone human chorionic gonadotrophin (hCG) is given to trigger final follicular maturation, which leads to spontaneous ovulation 32-36 hours later.

The advantages of this treatment are its low cost, ease of use and safety in women with breast cancer. Its disadvantages include a low pregnancy rate of 8-15% per cycle, the possibility of a twin or ectopic pregnancy, the possibility of ovarian hyperstimulation, failure of the medication, and other side effects, chiefly headache and general fatigue.

Unlike clomiphene citrate, letrozole does not alter the cervical mucus, so it does not need to be combined with intrauterine insemination.