My menstrual cycle: understanding periods and ovulation

The menstrual cycle marks half of a woman's life. From puberty to the menopause, a woman's hormones change regularly to prepare her body for pregnancy. Understanding how this process works can help to improve the chances of getting pregnant, or on the contrary, to avoid it. It may also be a way to better manage your menstrual symptoms and detect any problems in time.

The menstrual cycle marks half of a woman's life. From puberty to menopause, a woman's hormones change regularly to prepare her body for pregnancy. Understanding how this process works can improve the chances of becoming pregnant or help avoid it. It may also enable you to better manage your menstrual symptoms and detect any problems promptly.

The basics of the menstrual cycle

When a woman reaches puberty, she has monthly bleeding. This is known as menstruation. This bleeding results from the preparation of the inner layer of the uterus, which thickens during this period in preparation for a possible pregnancy. If the person is not pregnant, this thickened inner layer is shed; this may last between 3 and 8 days.

For some women, the menstrual cycle is regular and even predictable. For others, it is less regular. However, this second category represents a minority compared to the first. The duration between the 1st day of menstruation and the 1st day of the next menstruation can vary between 21 and 35 days. Thus, it is called a cycle.

The hormones involved in the menstrual cycle

Hormones are the conductors of the menstrual cycle. They cause changes in the female reproductive system, which can be classified into three stages. The control stage involves the hypothalamus and pituitary gland, the intermediate stage involves the ovaries and the execution stage involves the target organs (vagina, uterus and breasts).

The hypothalamus and pituitary gland are the main elements conditioning the functioning of the ovaries. These are two small endocrine glands located at the base of the brain. As well as stimulating the pituitary gland, the hypothalamus is responsible for secreting pituitary gonadotropin-releasing hormone. In response, the pituitary gland secretes two other hormones, namely luteinising hormone (LH) and follicle-stimulating hormone (FSH). These two elements act directly on the ovaries, which then secrete progesterone and oestrogen.

How the menstrual cycle works

The menstrual cycle comprises several phases, and the exact manifestation may differ for each woman. First, the follicular phase begins on the 1st day of menstruation and continues until ovulation. This phase is divided into two parts. First, the initial recruitment of the follicles occurs, with approximately 100 follicles starting to grow from primordial to tertiary follicles during each cycle. In the second part, growth occurs from antral to preovulatory follicles.

Simultaneously, secretion of oestrogen occurs from the ovaries. On the 1st day of menstruation, the rate of development is low. However, as the days pass, the follicle develops. This leads to many changes: the cervical mucus changes to provide a fertile environment for sperm, and the uterine lining thickens to accommodate a possible fertilised egg.

The other phase in the menstrual cycle is ovulation. In this case, the level of oestrogen indicates that the follicule is sufficiently mature. Therefore, a massive secretion of LH occurs. The tension of the fluid in the follicle increases, the wall ruptures and the egg is sucked out through the fringes of the fallopian tube. From there, it can survive for a maximum of 24 hours and a minimum of 12 hours. If no sperm fertilisation occurs, the oocyte degenerates.

From ovulation to the 1st day of the next menstrual period is the so-called luteal phase. During this period, the walls of the empty follicle begin to collapse, and the blood capillaries develop. This is known as the corpus luteum, the gland responsible for secreting oestrogen and progesterone (the so-called maternity hormone). Following this, two situations can occur. The lack of fertilisation leads to atrophy and degeneration of the corpus luteum. Abrupt cessation of oestrogen and progesterone secretion occurs. The thickened inner layer is then shed with bleeding. A new follicle begins to mature, starting a new cycle.

The other case is when the oocyte has been fertilised. In this case, the egg settles in the uterine lining. This is called implantation. This stage always occurs 1 week after fertilisation. When it is inside the uterus, the outer cell layer of the oocyte secretes the pregnancy hormone. This is chorionic gonadotropin (HCG). Its role is to keep the corpus luteum active, so it can secrete progesterone and oestrogen, which are essential for the remainder of the pregnancy. The placenta takes over at 3 months into the pregnancy.

How can we better understand the signals our body sends us?

To understand your cycle, you can follow it on a calendar. You must still take care to note the details, namely bleeding, symptoms (tender breasts, bloating and others), the beginning and end of the period, the flow, changes in mood, behaviour and so on. Over time, you will learn to detect irregularities well and simultaneously determine trends.

The cycle begins on the 1st day of your period and continues until the 1st day of your next period. Some women have short cycles (about 22 days). For others, it can be longer (40 days). Menstrual cycles vary in length. However, the length of the luteal phase is always fixed. Menstruation always occurs 14 days after ovulation. However, the date of ovulation can change. This depends on several factors, particularly the sex hormones.

These hormones have the power to inhibit or stimulate the production of LH-FSH. There may also be other factors, such as environmental influences, diet and the person's psychological and general health. However, after several cycles, you should have a good understanding of how your body works, especially if you keep a menstrual diary.