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:

1. It allows the ovary to liberate an ovum (or female gamete): this is ovulation. The ovum contains half of the future child's inherited traits, the half supplied by the mother.
2. It facilitates the meeting between this ovum and a spermatozoon (or male gamete), which supplies the paternal part of the future child's inherited traits. This is fertilization, in which a new human begins life.
3. It facilitates the implantation of the latter in the maternal nutritive area, the lining of the uterus, prepared for this purpose. This is the nidation, or implantation.

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:

1. A life-supporting action, by the transformation of the endometrium, which becomes soft and spongy after having thickened under the influence of estrogen during the first part of the cycle. One can compare it at this stage to a ploughed garden ready for planting.
2. The closing of the uterus, by contraction of the muscular fibers of the cervix, which closes and becomes firmer, and by the transformation of cervical mucus into a gelatinous plug (the garden gate is closed).
3. The signal to the hypothalamus to stop all orders destined for the pituitary, which therefore stops its own stimulation of the ovary: neither follicle maturation nor ovulation can now take place (the gardener prevents the production of new seeds).
4. The basal body temperature rises, 2 to 4 tenths of a degree Centigrade. This rise is useful for the future embryo's development (the gardener watches over the heat in the garden, as in a greenhouse).

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:

a) If there is fertilization, on ovulation day: the tiny embryo enters the uterus after traveling down the tube 5 or 6 days. It immediately takes roots in the endometrium and, through its roots, which will become the placenta, sends a chemical message (human chorionic gonadotrophin or HCG) into the mother's blood, ordering the corpus luteum to continue its four actions: hormonal stimulation of the endometrium, closing of the cervix, inhibition of pituitary stimulation and therefore of all ovulation, raising of the temperature. One can look for the child's HCG in the mother's urine for pregnancy.
b) In the absence of fertilization, the ovum dies within 24 hours after ovulation. But the corpus luteum is not informed: each cycle, it systematically "bets" on pregnancy and prepares the endometrium for implantation. When this implantation does not occur, the corpus luteum does not receive any stimulation from the HCG and ceases its activity about two weeks (a maximum of 16 days) after ovulation. This leads to discontinuation of the corpus luteum's four effects:
The endometrium, no longer nourished, is shed in menstruation. The cervical gelatinous plug becomes a liquid; the cervix opens and allows the menstrual bleeding to flow out. The hypothalamus can once more stimulate the pituitary and therefore the ovary. The temperature returns to its former low level.

Conclusion

1. The first part of the cycle is oriented, on the one hand, to ovulation and, on the other hand, to the male seed's reception, protection, and meeting with the ovum. The second part of the cycle is oriented to the child's reception and protection by the maternal environment. We all descend from these two successful processes of reception. Menstruation is only, as we have seen above, the sign of the failure of the fertility process.
2. The first part of the cycle is variable in length and is fertile around the time of ovulation. The second part of the cycle is of relatively constant duration (on the average, nine months or two weeks) and it is a sterile period, which means that no meeting between a spermatozoon and an ovum is possible at this stage. The cervix is closed and the ovaries inhibited. Thus, if the woman is pregnant, she cannot start a second pregnancy during these nine months; if she is not pregnant, she must wait until the end of the two weeks and for the fertile phase of the following cycle to undertake a pregnancy.
3. Every woman who is correctly informed can observe the signs of her cycle, i.e., notice the modifications of the cervical mucus, shift of the temperature, and changes in the consistency of the opening and of the position of the cervix. At the same time, she can understand the mechanisms and the meaning of these transformations. These three different ovulation tests will. be explained in the following chapters of this book.

References:

J.J. Billings. Natural Family Planning: The Ovulation Method (Melbourne).
J.J. Billings. Methode Billings: La Regulation Naturelle des Naissances (Edit. Paulines, Montreal, 1977).
J. Brown. Scientific Basis of the Ovulation Method (Melbourne).
S. Geller. Temperature Guide for Woman (Julliard).
F.M. Guy. Les Methodes d'Auto-observation (IREC, 1979).
E. Keefe. Self-observation of the Cervix to Distinguish Days of Possible Fertility (Dec. 1962).
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).
Nakamura (in Reader in NFP. Tokyo 1978, p. 149).
Serena Canada. Precis de la Methode Sympto Thermique (1977).
Serena Canada. Planning Your Family the S-T Way (1975).
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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