From puberty to the menopause, the ovaries produce a mature egg (ovum) approximately every 28 days. If the egg becomes fertilized, the ovaries also produce hormones – oestrogen and progesterone (sex hormones) – to prepare the lining of the womb to receive the fertilised egg(s) which grow(s) into a baby. This process is also under the control and signals of special horones and chemical produce from the parts of the brain called the pituitary and hypothalamus. This coordination of the activities of the hypothalamus, pituitary, ovaries and the lining of the womb, is what is responsible for the regular monthly changes that women have which results in the menstrual bleeding, if the egg produced is not fertilised. The whole series of activiutes and effects, occurring in the same way every monthly is called menstrual cycle. The menstrual cycle is the time from the first day of a woman’s period to the day before her next period. This process is very complex and whatever affects any part of the process can result in problems with the menstrual cycle and menstrual bleeding or periods, as it is usually called. The ability of a woman to get pregnant – female fertility -depends on the cycle occurring normally. For the purpose of timing, the first day of the menstrual cycle (Day 1) is the first day of menstrual blood loss. This is when the uterus begins to shed its lining and bleeding occurs. The last day (Day 21 – 35), is the last day of the cycle, the day before the bleeging starts again.
The most important of the special hormones controlling the menstrual cycle and therefore fertility are oestrogen, progesterone (from the ovaries), luteinizing hormone (LH) and follicle stimulating hormone (FSH) – from the pituitary gland. The FSH encourages few follicles (egg-containing ‘sacs’) in each ovary to grow each month, till one of them, the dominant ovum, becomes mature enough to be released, ready for fertlisation. When the egg is released, this is called ovulation, and it occurs, usually about 14 days before the next cycle begins – this usually corresponds to the mid-cycle. This first half of the ovarian cycle is known as the follicular phase and the second half is called the proliferative phase. Usually one egg is released each cycle, but occasional release of two or more eggs, is possible, in some individual, either because of hereditary or due to fertility treatment with medications. Common test for ovulation, rely on testing for high level of the luteinizing hormone (LH) excreted in the urine during ovulation. It is the sharp increase in the level of LH in the blood is necessary for ovulation, and it is passed in the urine. Any problem with the production of the LH may affect ability to ovulated, and therefore conception. At the time of ovulation there is a small rise in body temperature. This small rise can be used to indicate when ovulation occurs. Some women feel mild pain in the abdomen around the time of ovulation, lasting from a few minutes to a couple of hours. This is often called mid-cycle or ovulation pain (Mittelschmerz). The hormonal changes occurring during ovulation also causes the cervical glands to produce, very thin, see-through vaginal secretion or normal vaginal discharge. This can also be used to indicate ovulation, which some women use as part of their “safe period” method of contraceptive.
After ovulation, in the second half of the menstrual cycle, the hormones produced by the ovaries,
especially progesterone, together with oestrogen, help to prepare the lining of the womb to receive the fertilised egg, if there is conception. If ovulation did not occur in a particular cycle, the production of the progesterone is affected – this is the basis for testing the progesterone level in infertility work-up. This is because, after ovulation, it is the cells remaining in the ruptured follicle that multiply rapidly to form the corpus luteum, which produces higher amounts of progesterone and some oestrogen. These hormones act on the lining of the womb — it becomes thick and spongy and its glands secrete nutrients that can be used by the embryo if fertilization has occurred . If fertilization does not occur, towards the end of the cycle the process regresses and build-up of the lining of the womb stops, and the remaining glands and thickened lining containing blood vessels, are shed away, as menstrual loss. The process then repeats itself in the next menstrual cycle.