What is the menstrual cycle and what are its phases: EVERYTHING you need to know?

The menstrual cycle is defined as the time from the first day of a woman’s menstruation to just the day before her next period. Although the average duration of this period is 28 days, this is not exact and can range from approximately 21 to 45 days depending on each woman (while some experience shorter cycles, others have longer ones).

During the menstrual cycle, changes are experienced in the body, mainly in the uterus and in the ovaries. This is so because of the female sex hormones (estrogens and progesterone) which aim to prepare women for a possible pregnancy from the beginning of their reproductive stage with the first menstruation until menopause arrives.

In this article we are going to clear up your doubts with everything related to the menstrual cycle: What are its phases? How do hormones influence it? What kind of symptoms are experienced in each of its stages? What is the best time of the cycle to get pregnant? Very attentive!

What is the menstrual cycle?

  1. We can define menstruation or period as the desquamation of the inner lining of the uterus (endometrium) which is accompanied by bleeding. Monthly cycles occur in a woman’s fertile years, except during pregnancy, and range from puberty with the first period until it disappears with the onset of menopause.
  2. As we said before, menstrual cycles vary, they are considered regular if they appear between 25 and 45 days, and irregular if they fall outside of these parameters. Therefore, some women will have longer menstrual cycles while others will have shorter ones. The cycles do not have to be exact every month, there are women with cycles of different lengths and gynecologists consider it normal. Bleeding as such can last from 3 to 7 days and blood loss ranges from 15 to 75 cm3.

Female hormones, how do they influence the menstrual cycle?

In order to understand how the menstrual cycle works, first of all we must talk about the female sex hormones since they are in charge of regulating the entire process. All these hormones are not at zero in any phase, but they rise and are dominant at the moments that we are going to discuss below. These hormones are the following:

  • FSH (follicle-stimulating hormone): this hormone begins to be secreted at the beginning of the menstrual cycle and its primary function is to stimulate the ovary to generate the follicle that will be dominant in that cycle. But what are follicles? Very easy. These are structures responsible for housing ovules in different states of maturation.
  • LH (luteinizing hormone): this hormone is responsible for triggering ovulation once the follicle containing the egg has fully matured.
  • Estrogens: are hormones secreted by the ovary as the follicles develop. In addition to participating in the sexual development of women, estrogens are responsible for regulating the entire menstrual cycle.
  • Progesterone: this hormone is secreted by the ovary after ovulation. Its objective is to increase the endometrial thickness so that the embryo can implant and give rise to a pregnancy.

The four phases of the menstrual cycle that you should know

At the beginning of the menstrual cycle, the aforementioned sex hormones are in a basal state. This means that they present a minimum concentration because they have not yet begun to be produced. From this moment, it is possible to distinguish between various phases within the menstrual cycle based on hormonal levels and the changes they experience.

According to this, the menstrual cycle is made up of four phases or stages:

Menstrual phase

The menstrual cycle begins with the arrival of the rule. Menstruation triggers bleeding that is the product of the expulsion of the endometrium. The endometrium is the inner lining of the uterus and is renewed every month in order to accommodate a pregnancy. If there is no embryonic implantation, the endometrium is shed. The usual duration of this phase is 4 to 7 days.

Follicular phase

  • This phase is also known as proliferative or preovulatory and in it the growth of the ovarian follicles occurs. It develops from the beginning of menstruation until ovulation takes place.
  • Each woman is born with an ovarian reserve of approximately 500,000 primordial follicles in her ovaries. These follicles remain in a waiting state until they are selected to develop in each menstrual cycle. It is precisely the increase in the FSH hormone that causes several of these follicles to begin to grow.
  • Of all the follicles that develop in a menstrual cycle, only one of them is capable of fully maturing, thus becoming the final preovulatory follicle or also known as the Graafian follicle. The rest of the follicles are blocked and end up degenerating.
  • On the other hand, estrogens also make their appearance at this stage, contributing to the creation of abundant, watery and elastic cervical mucus that has the function of facilitating the entry of spermatozoa. Estrogens also act on the endometrium, favoring its thickening.

Ovulatory phase

  1. In this phase, estrogen levels continue to increase (they reach their peak while the progesterone level begins to rise) causing the woman’s body to produce luteinizing hormone (LH) which is responsible for releasing the egg from that hormone. cycle and make it come out of the ovary. It is at this time that ovulation occurs (approximately around day 14 of the menstrual cycle).
  2. Once released, the egg travels through the fallopian tubes until it reaches the uterus. The usual thing is that the egg survives up to 24 hours outside the ovary, so if during this period of time it comes into contact with a sperm, it can be fertilized and a pregnancy can occur.
  3. With regard to spermatozoa, they have the ability to survive in the woman’s body for between 5 and 7 days. This means that if a woman has had unprotected intercourse up to five days before her ovulation occurs, there is a risk that she could become pregnant.
  4. In the event that pregnancy does not occur, the unfertilized egg loses its ability to be fertilized and its shape in the fallopian tubes.

Luteal phase

  • The luteal phase is also known as the secretory or postovulatory phase and takes place just after ovulation until the end of the menstrual cycle, that is, until menstrual bleeding occurs again.
  • Throughout these days, the follicle left by the egg (called the corpus luteum) inside the ovary begins to produce progesterone in order to continue preparing the uterus for a possible pregnancy. During this phase, it is common for women to begin to experience the symptoms of Premenstrual Syndrome, which include breast swelling, sudden mood swings, and abdominal swelling.
  • When fertilization does not take place, the follicle contracts inside the ovary and estrogen and progesterone levels begin to drop. This causes the endometrium to be eliminated giving rise to menstruation and the beginning of the next menstrual cycle.
  • In the event that the egg is fertilized, it will stick to the walls of the uterus and the body will begin to produce hCG. This is a hormone in charge of keeping the follicle producing estrogen and progesterone in high amounts to sustain the endometrium until the placenta is formed.

What symptoms does a woman experience in each phase of the menstrual cycle?

Each phase of the menstrual cycle is characterized by the appearance of specific symptoms, although by far the most significant are those that occur during the luteal phase. At this stage, the woman begins to suffer the discomfort of the well-known Premenstrual Syndrome (SPM). These discomforts appear during the 7 or 10 days prior to the arrival of the period and are maintained during the first hours or even days of menstruation. These symptoms are as follows:

  • Emotional swings.
  • Pain in the abdomen.
  • Sensitive and swollen breasts (breast pain).
  • Colic and nausea.
  • Fluid retention.
  • Sudden mood swings.

However, the ovulation phase also causes the woman to be much more sensitive. In addition, during this stage it is also common for the dreaded and hated ovarian pain to appear. However, it must be remembered that in the face of any type of intense pain, the ideal is to go to the gynecologist. We should not normalize the pain since, behind it, there may be other problems such as endometriosis or Polycystic Ovarian Syndrome.

What is the best time of the menstrual cycle to get pregnant?

The fertile days of the woman, that is, those in which the chances of a pregnancy occurring are much higher, are those that correspond to the ovulatory stage or phase. Ovulation usually takes place in the middle of the menstrual cycle, approximately on days 13-14-15, as long as the woman has regular menstrual cycles of 28 days.

To calculate the fertile period more accurately you can use the calendar technique also known as the rhythm method. The fertile stage includes the day of ovulation itself, plus three days before and three days after. Remember that this only applies to regular menstrual cycles. In the irregular it is always more complicated to calculate these days of fertility, however there are certain signals from the body that can help in the arduous task:

  • During the fertile period, the woman secretes a transparent discharge very similar to the white of an egg. Before ovulation, a woman’s vaginal discharge is mucous, while in the second phase of the menstrual cycle it is thicker and less abundant.
  • In this phase the basal body temperature also changes since it increases slightly during ovulation.
  • On the other hand, pimples can also appear since the skin becomes oilier in this period.
  • Increased libido. This is another symptom that indicates that the fertile days have arrived due to the increase in hormonal levels, so the woman will have more sexual appetite.
  • There is an increase in the sensitivity of the breasts.
  • Mild pain is experienced in the area of ​​the uterus similar to a mild and temporary colic.
  • It is also possible to detect ovulation using a test that you can buy at the pharmacy.

Causes that make the menstrual cycle become irregular

Here are the causes that can cause an irregular menstrual cycle:

  • Adolescence or first menstruation: in these stages it is normal for the rule to be irregular.
  • Premenopause: due to multiple hormonal changes.
  • Eating disorders (such as anorexia nervosa) and sudden weight loss.
  • Too intense physical activity.
  • hyperthyroidism _
  • Polycystic ovaries.
  • Stress, nerves or emotional disorders.
  • Polyps or tumors in the female reproductive system.
  • Post-pregnancy period.

If you have irregular menstrual cycles or your period has been delayed for more than three months, it is essential that you consult your gynecologist as it could be due to more serious health problems.

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