The menstrual cycle refers to the period between the first day of menstruation and the first of the next period.
During the period of the menstrual cycle, the body undergoes changes that prepare it for a possible pregnancy.
The first menstruation is called menarche and in the first two or three years it is normal for the cycles to be a little irregular. Over time, they become more regular and tend to stabilize until they reach 40-45 years.
From this age on, the cycles become irregular again until the menopause phase, when the woman stops menstruating.
Stages of the menstrual cycle
There are two main phases of the menstrual cycle that differ, the follicular phase and the luteal phase. One can still recognize a third phase, ovulatory, characterized by the moment of ovulation.
The duration of the menstrual cycle is around 28 days , although there are shorter cycles of 21 days and longer cycles of up to 35 days, also considered normal.
1. Follicular Phase
The first phase is called the follicular phase, which lasts approximately 14 days , varying from 9 to 23 days. This phase gets its name because the ovarian follicles are in the process of development.
But, what are ovarian follicles? They are found in the ovaries and harbor immature eggs that will be released gradually over the woman’s reproductive life.
The follicular phase begins on the first day of bleeding until the egg is released, the ovulation phase. Menstruation, a period of bleeding, lasts an average of 5 days, although it can range from 3 to 7 days.
In the first days of the follicular phase, there is a large production of the hormone FSH (stimulating follicle), responsible for stimulating the ovaries to produce mature eggs.
As follicles mature, there is also high production of the hormone estrogen, resulting in thickening of the endometrium and formation of vessels, conditions that make the uterus ready to receive the fertilized egg and start pregnancy.
At the end of the phase, the main follicle continues its development and growth, secreting estrogen faster and faster, leading to a peak of estradiol around the tenth day.
In general, the main follicle continues to develop and increases in size. Estrogen secretion remains high, ensuring that the egg is in a condition to be released.
Another characteristic is the change that occurs in the mucus in the cervix, which becomes thin and watery. All of these changes consist of preparing the uterus for the possible arrival of sperm and consequent fertilization.
2. Ovulatory Phase
The ovulatory phase consists of releasing the mature egg and being able to be fertilized, which goes to the fallopian tubes or fallopian tubes and goes to the uterus. This process consists of ovulation.
The day of ovulation varies depending on the length of the cycle. In many cases, it occurs on the 14th day of the cycle . However, this is not a rule and most women ovulate on different days of the cycle.
The egg has a short life span, around 24 hours. For pregnancy to occur it is necessary to have sex in the woman’s fertile period. Sperm can remain viable for up to 5 days in the female body.
For this reason, it must be considered that sexual intercourse without the use of contraceptive methods and up to 5 days before ovulation may result in pregnancy.
3. Luteal or luteal phase
The luteal phase begins with the formation of the corpus luteum, it comprises the period from ovulation to the first day of the next menstruation.
The formation of the corpus luteum or yellow body occurs after ovulation due to the transformation of the walls of the ovarian follicles that become a secretory structure of the hormone progesterone, the most active in this phase.
In general, the luteal phase lasts around 12 to 16 days . The corpus luteum may deteriorate or remain active, indicating a possible pregnancy.
Progesterone promotes greater lining of the endometrium, preparing the uterus to receive the fertilized egg and fixation of the zygote.
If nesting does occur, the production of hCG (Human Chorionic Gonadotrophin), known as the pregnancy hormone, begins, keeping the corpus luteum active.
If fertilization does not occur, the corpus luteum degenerates and a new cycle begins with the onset of menstruation.
Menstrual Calendar
The menstrual calendar or table is a method used to predict the likely day of ovulation, that is, the woman’s most fertile period.
For example, if the menstrual cycle is 28 days, ovulation occurs on the 14th day after the first day of bleeding.
However, considering the lifetime of the sperm, it is necessary to consider a few days before ovulation as highly probable for the risk of pregnancy.
Sexual intercourse should be avoided five days before and five days after the likely day of ovulation. On the other days of the cycle, the chances of getting pregnant are lower.
It should be noted that this method is not safe to prevent unwanted pregnancies and also does not prevent against Sexually Transmitted Diseases.