The menstrual cycle refers to the period from the first day of menstrual bleeding to the onset of the next period, which normally lasts 21-36 days. Bleeding duration of 3-to 7 days is normal. Somewhere in the middle of the cycle, ovulation occurs.
Most women who have such regular monthly cycles, painful periods and premenstrual syndrome (breast tension, pain in the lower abdomen) also ovulate. 5% of such women nevertheless have anovulatory cycles (cycles in which there is no ovulation), as well as most women with irregular and prolonged cycles with abundant, irregular and painless bleeding.
Most women with regular cycles will have an anovulatory cycle once or twice a year, just as most women with irregular bleeding will ovulate several times a year.
Anovulation does not mean the absolute impossibility of getting pregnant, but these women have a reduced chance of pregnancy since most women ovulate 10-12 times a year, and they only ovulate once or twice. If the other findings are correct, when a woman with irregular cycles ovulates, her chance of pregnancy is the same as for a woman with regular periods.
According to the World Health Organization (WHO), there are three types of anovulation:
WHO type I – hypogonadotropic hypogonadism
WHO type II – normogonadotropic anovulation
WHO type III – hypergonadotropic hypogonadism
In hypogonadotropic hypogonadism (type I), which is most often the result of stress, exercise or an important weight loss , after correction of the problem that led to anovulation, stimulation of ovulation is usually required.
Hypergonadotropic hypergonadism (type III) is a consequence of premature exhaustion of the ovaries in women. Patients with such condition respond to conventional therapy, and egg donation is usually the only therapeutic option.
There is also a group of women with anovulation caused by hyperprolactinemia (increased prolactin levels in the blood), who are successfully treated. Anovulation caused by thyroid dysfunction is treated by normalizing thyroid function, after which ovulation is established.
Induction of ovulation in women with anovulation due to dysfunction of the hypothalamus and pituitary gland (WHO type II, most commonly PCOS, polycystic ovary syndrome) is particularly difficult.
It is potentially dangerous due to the development of numerous follicles and ovarian hyperstimulation syndrome; and because of the possibility of multiple pregnancies, which carries numerous risks for the fetus.
At the same time, often the woman will not even respond to the therapy.
According to the recommendation of the European Society for Human Reproduction and Embryology (ESHRE), the goal of ovulation induction in women with PCOS is mono follicular ovulation (creation of one follicle) with maximum reduction of the risk of ovarian hyperstimulation syndrome and multiple pregnancies.
