A Normal Menstrual Cycle: What Happens in Your Body?

On which days do you have the greatest chances of getting pregnant and on which days should you be prepared for unexpected changes in mood and well-being? All these questions will be answered by understanding what happens in your body during each menstrual cycle.

From menstruation to menstruation

The menstrual cycle is a series of cyclical changes that occur in the body of a woman of childbearing age, determining readiness for a possible pregnancy. Approximately once a month, the inner walls of the uterus are covered with a soft porous tissue (endometrium), which has the ability to hold a fertilized egg. If fertilization does not occur and pregnancy does not occur, the outer layers of the endometrium are shed and shed, causing bleeding - this is menstruation. This cycle repeats itself over and over again. Monthly menstrual bleeding (also called menstruation or menstrual period) becomes the norm for every healthy woman from the early teenage years (from the onset of puberty) until about age 50, when the childbearing period ends and menopause occurs.

The menstrual cycle is calculated from the first day of menstrual bleeding (1st day) to the first day of the next menstrual bleeding. While the average length of a menstrual cycle is 28 days, it's perfectly normal for your cycle to be shorter or longer. In some women, the menstrual cycle is irregular and its duration changes every time. Such a phenomenon is not always a deviation from the norm and should not cause concern (if you feel completely healthy), but you should consult with your gynecologist about this issue.

Dependence of the duration of the menstrual cycle on the age of the woman:

• Menstrual cycles in teenagers can be much longer (up to 45 days) - over the course of several years, their duration will decrease.
• At the age of 25 to 35, most healthy women have regular menstrual cycles, mostly lasting from 21 to 35 days.
• A woman typically has the shortest and most frequent menstrual cycles between the ages of 40 and 42.
• In the next 8 to 10 years, approximately between the ages of 42 and 50, a woman's menstrual cycles become much longer, less regular - until the cessation of menstruation and the onset of menopause.

Three phases of the menstrual cycle

The phases of the menstrual cycle are determined by the level of special hormones: follicle-stimulating hormone, estrogen, luteinizing hormone and progesterone. The main and defining changes in a woman's body during the menstrual cycle concern the ovaries and endometrium. As for the functioning of the ovaries, follicular, ovulatory, and luteal phases are distinguished for each menstrual cycle, and for the endometrium, there are menstrual, proliferative, and secretory phases. And now about all these complicated terms - clear and simple.

Menstrual period

On the first day of the menstrual cycle (with the onset of menstruation), the outer functional layers of the endometrium — the soft porous tissue lining the inner walls of the uterus — are separated and rejected, which is accompanied by bleeding. Normally, a healthy woman's period can last from 5 to 7 days. No matter how abundant the bleeding seems to you these days, in fact, a woman loses no more than 25-30 cubic meters of blood during menstruation. see The secretion of the mucous glands of the uterus is added to it - thanks to this secretion and the enzymes it contains, menstrual blood does not coagulate. You need to know about this, because blood clots in menstrual discharge can indicate uterine bleeding or other pathologies, so in this case you must consult a gynecologist.

The heaviest bleeding is possible in the first three days of menstruation. These days, you may experience painful cramping in your lower abdomen, as well as pain in your pelvic joints, legs, and back. Even convulsions are possible - from mild to quite serious. Pain in the lower abdomen is caused by spasms of the walls of the uterus, which contribute to the rejection of the endometrium. Any manifestations of PMS (premenstrual syndrome) that made life a little difficult for you in the last days before the start of menstruation will disappear already in the first days of the menstrual cycle.

Follicular phase

The follicular phase can last from 7 to 22 days, but the average for a healthy woman of fertile age is 14 days. At this time, the final maturation of the dominant follicle takes place in the ovary, in which the egg is formed. As a rule, with each menstrual cycle, a woman forms and releases one mature egg (but there are exceptions - proof of this is multiple two-egg pregnancy). At the same time, a layer of new endometrium grows inside the uterus (proliferative phase) — the woman's body is preparing for a possible pregnancy.

The last five days of the follicular phase plus the day of ovulation are the fertilization period. That is, if you have unprotected intercourse on these days, you will most likely get pregnant. This should be known to those women who want to have a child, and those for whom pregnancy is not currently in the plans. Ask your gynecologist to help you determine the exact fertile "window" of your menstrual cycle.

Ovulatory phase

During the entire follicular phase, a dominant follicle, which is called a Graafian follicle, is determined and continues to grow. When he reaches maturity, the ovulatory phase begins, which lasts about three days. In this shortest phase of the menstrual cycle, in 36-48 hours, several waves of luteinizing hormone release occur in the woman's body - thanks to its sharp increase in the plasma, the development of the Graafian follicle is completed, its walls rupture and release a mature egg (ovulation itself).

When ovulating, some women experience minor bleeding, pain or discomfort in the lower abdomen - these are usually normal signs of ovulation, but you should still tell your gynecologist about them.

Lutein (premenstrual) phase

This phase begins on the day of ovulation — the day when a mature egg is released from the dominant follicle. This can happen anytime between the 7th and 22nd day of a normal menstrual cycle in a healthy woman. The luteal phase lasts until the start of the next menstrual bleeding, usually 13-16 days. If the egg is fertilized, the uterus prepares for its implantation in the tissues of the endometrium and pregnancy occurs. The term of such a pregnancy will be calculated from the 1st day of this menstrual cycle (not from the day of ovulation or possible fertilization - this is what many expectant mothers mistakenly believe).

These days, the so-called corpus luteum — the modified Graafian follicle from which the egg was released — is responsible for the complex processes inside your body. Lutein pigment accumulates in its cells, due to which it acquires a yellow color. The corpus luteum secretes hormones: progesterone, estradiol and androgens. It is precisely because of the high level of progesterone and estrogen that changes occur in the outer layers of the endometrium, which begins to secrete and prepare for the implantation of a fertilized egg (secretory phase). During pregnancy, the corpus luteum will continue to produce progesterone until the placenta develops in the uterus, after which it will independently produce a sufficient amount of estrogen and progesterone.

If the egg is not fertilized and pregnancy does not occur, the level of progesterone and estrogen gradually decreases, the outer layers of the endometrium begin to break down and in a few days are rejected by the walls of the uterus, which causes another menstruation. A new menstrual cycle begins.

Many women experience various unpleasant premenstrual symptoms during all or part of the luteal phase. This phenomenon was called premenstrual syndrome - PMS. You may feel tense, irritable, or overly emotional and vulnerable. You will also experience more fatigue and loss of energy, which is also normal. Among the physiological manifestations of premenstrual syndrome, swelling, sensitivity and pain in the chest, and the appearance of acne on the skin are the most common. A day (or more) before the start of your next period, you may experience cramps in your stomach, back, or legs. Some women experience PMS with headaches, diarrhea or constipation, nausea, dizziness, and even fainting.

If premenstrual symptoms are interfering with your normal life, talk to your gynecologist about PMS management options.