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The woman’s menstrual cycle: a precise calendar
D1 to D14: the ovum is preparing. This is the follicular or pre-ovulatory phase
The menstrual cycle begins on the 1st day of menstruation. This first phase begins with the onset of bleeding which lasts an average of 3 to 5 days (but may last only 2 days or extend up to 6 days). In the event that fertilization does not take place, the level of sex hormones (progesterone) drops sharply and the upper layer of the uterine lining, filled with blood, is eliminated through the vagina. Within days of the onset of bleeding, the lining of the uterus begins to rebuild, under the effect of the increased production of estrogen. These hormones are secreted by the ovarian follicles, small cavities on the surface of the ovary in which the egg develops.
Along with the removal of the lining of the uterus (also called the endometrium), the process of preparing the uterus to receive the fertilized egg begins again. At the end of this phase, only one of the follicles present in the ovary matures and expels an oocyte.
What will be the day of ovulation?
How to calculate the exact day of ovulation? Ovulation usually occurs at the end of the follicular phase, on the 14th day of a 28-day cycle, 38 h after peak secretion of a so-called luteinizing hormone (LH). Ovulation lasts 24 hours and corresponds to the release of an oocyte from the ovary (the left or the right, regardless of the cycles). The oocyte, which has become an ovum, can then be fertilized by a sperm, then descend into the fallopian tube to implant in the uterus.
Note that after sex, sperm can survive for up to 4 days in your reproductive organs. Since the lifespan of the egg is around 24 hours, your chances of success extend to around 4 days around ovulation.
D15 to D28: implantation is preparing. This is the luteal, post-ovulatory or progestational phase
After ovulation, the ovary secretes another hormone, progesterone. Under its influence, the uterine lining thickens and the blood vessels branch out, which prepares the lining to accept an embryo in the event of fertilization.
If there is no fertilization, the part of the ovary that secretes progesterone, called the corpus luteum, atrophies after 14 days. The progesterone level then drops sharply and causes desquamation and evacuation of the uterine lining. These are the rules that mark the start of a new cycle.
Menstrual cycle: and in case of pregnancy?
If there is fertilization, the production of estrogen and progesterone continues and the uterine lining thickens even more. The fertilized egg can then implant itself in the uterine lining, which does not shed and does not cause menstruation. It is implantation, in other words the beginning of pregnancy. This implantation occurs 6 days after ovulation. Pregnancy is manifested by hormone levels that are very different from those of the female menstrual cycle.
Long, short, irregular: menstrual cycles of varying duration
To keep it simple and have a precise reference, the day you have your period is the first day of the cycle. To count its duration, you therefore go until the last day before the next period. What is the “normal” length of a cycle? As a little anecdote, we use a 28-day menstrual cycle in reference to the lunar cycle which lasts 28 days. Hence the Chinese expression when you have your period: “I have my moons”. However, the length of a menstrual cycle can vary between women and between periods of life. There are cycles shorter than 28 days, cycles longer and even cycles without ovulation, or anovulatory.
Some cycles may be disturbed. It can also happen that your periods disappear as a result of psychological trauma or significant weight loss. If in doubt, do not hesitate to talk to your doctor, midwife or gynecologist.
Temperature and female menstrual cycle
The temperature changes throughout the cycle. During the follicular phase, it is below 37 ° C and varies little. Just before ovulation, it drops and is at the lowest point of the cycle. Then, it rises again, often above 37 ° C and remains at this level for the duration of the last phase of the menstrual cycle. When there is no fertilization, the temperature drops to its normal level, just before the onset of menstruation. In the event of pregnancy, the thermal plateau continues.
Which application to calculate your menstrual cycle?
To find your way around your menstrual cycle, there are now smartphone applications that guide you. It indicates the date of her last period, and possibly other criteria such as the observation of cervical mucus, the use of ovulation tests or symptoms of a possible premenstrual syndrome (sore breasts, moodiness, retention water, headaches…). Let us quote in particular Clue, Glow, Natural Cycles, Flo or Menstrual Perio Tracker, u again Eve. Note that they can also be used to navigate your cycle, to try to get pregnant and identify her fertile period or by trying to avoid pregnancy through abstinence around the date of ovulation.