Natural Family Planning: Nature's Way - God's Way

32. A Few Reminders about the Menstrual Cycle

To understand the human fertility mechanisms and the principles for their control, a few anatomical and physiological references are necessary.

A woman's genital system basically includes the following:Two sexual glands or gonads, the OVARIES (0) containing numerous little pouches, the Follicles (f); an Ovum (ov) develops in each of the latter.

The UTERUS (U)or womb, a hollow muscular organ. The internal walls of the uterus are covered with a mucous lining called the Endometrium (end.). The VAGINA (V), a cylindrical muscular corridor leading from the Vulva (Vu) to the entrance of the Uterus, the Cervix (c), which is furrowed with cavities or cervical crypts (cc).

The Fallopian Tubes (t), canals linking the upper end of the Uterus to the Ovaries.

What is the Ovarian Cycle? - or the menstrual cycle, or the feminine cycle?

It is a dynamic process, repeated regularly in most women between the age of 13 and about 45-50. This process takes place in the ovaries and uterus, and its essential goal is the transmission of life. This process has a triple effect:

The cycle's aim is therefore pregnancy and a child. if this aim is not achieved, all the changes are interrupted: the shedding of the prepared endometrium results in a bleeding, the menstrual period (or menses) underlining the uselessness of the fertility process started at the beginning of a particular cycle.

Thus, a cycle, in the broad sense of the word, can last from the first day of the menses until delivery, when the process is completed; until the first day of the following menses, when the process is incomplete.

First Objective: Allow the ovary to release an ovum: this is the first part of the ovarian cycle.

A few days after the beginning of menses (and this part of the cycle is variable in length) the ovary receives from an area in the brain (the hypothalamus), through a hormone secreted by the pituitary, the order to mature a follicle and its contents, ie., the ovum. In fact, the pituitary sends a double order to the ovary: it consists of pituitarian gonadotrophins, FSH and LH.

Responding to this double stimulation (FSH and LH the follicle matures, develops, and manufactures a hormone, estrogen, which is poured into the blood. The level of estrogen regularly increases up to maximum, the estrogen peak. The peak of FSH and LH reacts to the estrogen peak and causes the follicle to explode. The mature ovum is projected into the tube.

The follicle's maturation takes about eight days; the location of ovulation after the beginning of the cycle depends on when the maturation itself started. The ovum survives 24 hours, at most, after ovulation. It is important to remember that the day of ovulation represents the end of the first part of the cycle, and that this part is variable in length.

Second Objective: Facilitate the meeting between the ovum and the spermatozoon.

It is clear that this meeting is possible during a limited period of time, the length of the ovum's life, i.e., about 24 hours.

But the fertile phase lasts longer than that, since nature makes it possible for the spermatozoa to be ready in advance.

About a week before ovulation, under the influence of the estrogen increasingly secreted by the follicle, the cervix softens and opens up, and its crypts start to secrete cervical mucus.

Cervical mucus, similar in appearance to raw eggwhite, becomes more and more clear, stretchy, stringy, and lubricative as the days go by, flowing into the vagina down to the vulva. This mucus will serve the eventual spermatozoa as a guide.

Assisted by cervical mucus, the spermatozoa deposited in the vagina during intercourse ascend to the cervix, where some will be stored, protected, stimulated in the cervical crypts. During the hours and days following intercourse, they leave in small groups for the inside of the uterus, and then the tubes, where an ovum may be waiting.

Thus, extended survival of the spermatozoa is a function of the continuing availability of a favorable cervical mucus.

Third Objective: Facilitate the implantation of a new child in the maternal uterus: this is the second part of the ovarian cycle.

When the ovum leaves the ovary to. enter the tube, a small temporary gland called the corpus luteum develops in its place in the follicle.

The corpus luteum (or yellow body), which we can compare to a gardener employed at each ovulation to prepare the garden (or uterus) pours into the blood the second female sexual hormone (or progesterone), intended first for the uterus but also for the brain * Progesterone joins the estrogen that the walls of the follicle are still producing.

Progesterone produced by the corpus luteum has four effects:

These four progesterone actions start as soon as the corpus luteum is in place, i.e., at ovulation. Subsequently one of the following two processes takes place:



  1. J.J. Billings. Natural Family Planning: The Ovulation Method (Melbourne).
  2. J.J. Billings. Methode Billings: La Regulation Naturelle des Naissances (Edit. Paulines, Montreal, 1977).
  3. J. Brown. Scientific Basis of the Ovulation Method (Melbourne).
  4. S. Geller. Temperature Guide for Woman (Julliard).
  5. F.M. Guy. Les Methodes d'Auto-observation (IREC, 1979).
  6. E. Keefe. Self-observation of the Cervix to Distinguish Days of Possible Fertility (Dec. 1962).
  7. E. Keefe. Cephalad Shift of the Cervix Uteri: Sign of the Fertile Time in Women (Int. Rev. of NFP. Collegeville, MN, Vol. 1, No. 1, 1977).
  8. Nakamura (in Reader in NFP. Tokyo 1978, p. 149).
  9. Serena Canada. Precis de la Methode Sympto Thermique (1977).
  10. Serena Canada. Planning Your Family the S-T Way (1975).
  11. WHO Colloquium. Geneva 1972. Cervical Mucus in Human Reproduction.

by Michele Guy, M.D.

Michele Guy, M.D., is Technical Assistant (with her husband) of "Action Familiale" in Mauritius (1964-1966); Assistant in the Maternity ward of the General Hospital of Grenoble (France), Family Planning and Family Education Centre of University Hospital of Grenoble.

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