Human Reproduction: The Marvelous Machine at Work

Author: A.L.L.


American Life League

How is the suspension of procreation to be brought about? Not by immoral and artificial checks that are resorted to in Europe, but by a life of discipline and self-control.

In the light of what I have said, birth control by contraceptives and the like is a profound error.

Birth regulations or restriction by artificial means is a calamity of the first grade whether we know it or not. It is bound to degrade the race if, it becomes universal, which, thank God it is never likely to do.

It is a sin to bring forth unwanted children, but I think it is a greater sin to avoid the consequences of one's own action. It simply unmans man.

                                                                                               Mahatma Gandhi.[1]

Anti-Life Philosophy.

Even those religionists who believe in a God must acknowledge that, if He made man in His image, and if He made man with the ability to reason, then surely it is allowable to be able to use that ability to reason to control our bodies and make them do what we want them to do.


The abortion debate is relentlessly heating up and expanding every day.

One of the most critical areas in this struggle is the gradual introduction of abortifacient methods of "birth control;" the intra-uterine device (IUD), the low-dosage birth control pills, NORPLANT, Depo-Provera, and the outright abortion pills like RU-486 and Cytotec.

Several parallel fields of controversy are gaining more public attention as well. These include in-vitro fertilization (IVF), other infertility "treatments," surrogate motherhood, and even artificial wombs.

In order to be able to approach these subjects with a better view as to how they are related to abortion and natural and artificial methods of contraception, it is important to understand exactly how they work to prevent or to end pregnancy. In order to do this, one must have a basic working knowledge of the human reproductive system and how it functions.

The Female Reproductive System.

It was you who created my inmost self, and put me together in my mother's womb; for all these mysteries I thank you: for the wonder of myself, for the wonder of your works.

My frame was not hidden from You, when I was made in secret, and skillfully wrought in the lowest parts of the earth.

Your eyes saw my substance, being yet unformed.

And in Your book they all were written, the days fashioned for me, when as yet there were none of them.

                                                                                                    Psalms 139:13-16.

The Uniqueness of Woman.

God instructed us as a race to go forth and multiply. Why, therefore, did He make human women unique among all females?

Women are the most infertile mammals on earth in terms of total percentage of fertile time. Every Christian believes that God does everything for a purpose. Why, therefore, did He create woman with a fertile/infertile cycle?

There is a solid Biblical reference supporting periodic abstinence. Leviticus 15:19,28 recalls that the Jews prescribed two weeks of abstinence at the beginning of a woman's cycle because she was considered to be 'unclean' during this time. This also meant that sexual relations would be resumed at the time of maximum fertility, and this insured the survival of the Tribes.

A woman's reproductive organs comprise an amazingly complex system that performs the astounding task of self-reproduction. If this sounds unimpressive, imagine how difficult it would be for human beings to construct an automobile or a computer that could reproduce itself.

Six parts of the woman's reproductive system are directly involved in reproduction, and are of particular interest;

(1) the ovaries
(2) the Fallopian tubes
(3) the uterus
(4) the cervix
(5) the vagina
(6) the breasts

These vital organs are described in the following paragraphs.[2]

The Ovaries.

The ovaries are a classic example of natural redundancy at work. While men manufacture sperm continuously, each newborn girl possesses all of the eggs she will ever need at birth, stored safely in her ovaries.

Each one of these 30,000 or so eggs is contained in a protective package called a follicle. These eggs do not mature until puberty. All through the fertile years, at intervals of anywhere from 24 to 35 days, a follicle (or rarely, follicles) will ripen and eject its egg. This process is commonly referred to as ovulation, and usually occurs in alternating ovaries.

The average age of first menstruation/ovulation (menarche) was about 17 to 18 years a century ago. Today, due to better health care and diet, the average age of first menstruation/ovulation is about 13 years of age. Due to the same reasons, the cessation of ovulation at menopause has now been moved back to an average age approaching fifty.

The Fallopian Tubes.

The Fallopian tubes serve as a conduit for the ejected egg as it travels from the ovary to the uterus. These tubes are about five inches long, are about twice the diameter of a human hair, and are extremely delicate. For this reason, many problems related to infertility are grounded in blocked or damaged Fallopian tubes. Many infertility treatments, including in-vitro fertilization (IVF) and gamete intra-fallopian transfer (GIFT), are designed to bypass Fallopian tube blockages.

Conception of a new human being (the fertilization of the egg by the sperm) takes place in the Fallopian tube.

The Uterus.

Although many Neofeminists seem to have a fixation on this organ (U.S. out of my uterus!"), not ten percent of them know exactly how it functions.

The uterus is the most powerful muscle in either the male or the female body. It is also the residence for the unborn child from implantation to ejection by natural or unnatural means.

The uterus begins a pregnancy in approximately the shape and size of small pear. The uterine lining that is constructed each month to sustain new human life, and which is maintained by the follicle's progesterone, is called the endometrium. The newly conceived human life (blastocyst) implants in this lining and receives its nourishment here.

If no conception takes place, the endometrium is discharged through menstruation about two weeks after it was formed.

The Cervix.

The cervix joins the vagina (outer sexual organ) to the uterus. It is about one inch long, and its lower end has an opening called the os (Latin for "mouth"). The cervix is lined by glands that secrete mucus when prompted by the female hormone estrogen.

The Vagina.

The external female sexual organ. Sperm deposited in the vagina enter the cervix and eventually progress to the uterus and into the Fallopian tubes, where conception may occur. In the area of the vagina are the clitoris, a pea-sized organ located above the opening to the vagina, and the labia, the flaps of shin covering the vagina's opening. The vulva consists of outer sexual organs at the opening of the vagina.

The Breasts.

Although they are not directly involved in actual human conception, stimulation of the breasts can suppress ovulation and thus block fertility for a certain period after birth when the mother is breastfeeding her child.

The Reproductive System at Work.


A brief bio-historical description is usually the easiest way to understand human reproduction. Therefore, this section describes the female reproductive system at work from the onset of menstruation to post-menopause.[2]

The Beginning and End of Fertility.

When a girl reaches sexual maturity, she has her first menstrual cycle, sometimes referred to as the 'menarche.' This repeating process can begin as early as ten, and usually occurs by the age of fifteen. The menstrual cycle normally continues until anywhere from age 40 to age 60, but ovulation and menstruation tend to be more intermittent near the end of menstruation (pre-menopause).

When fertility ceases entirely for a fixed period (usually six to twelve months), fertility has ended. Lately, however, scientists are experimenting with assisted pregnancy even after the menstrual cycle has ended naturally.

The Fertility Cycle.

On the average, women have a complete cycle every 28 days. This may vary from as little as two weeks to more than two months for any individual woman, especially near the beginning or end of fertility. Some women are extremely regular, and others have very irregular cycles. When a woman takes oral contraceptives (the birth control pill), her natural cycle is overpowered by the hormones they contain and usually "settles" into a regular 28-day cycle.

Each woman has a relatively regular luteal phase. This is the length of time between ovulation and the following menstruation, and may vary from ten to fifteen days between women.

Irregularities in cycle length may be caused by sickness, stress, and heavy physical activity. If exercise is heavy enough, as in women marathon runners, the menstrual cycle may temporarily cease altogether, a condition known as amenorrhea. This condition may also be caused by breastfeeding and various illnesses.

The fertility cycle is said to begin on the first day of menstruation. For the first few days of the cycle, fertility is relatively low. This is followed by the fertile phase, which, regardless of the length of a woman's cycle, is usually five to seven days in length. This figure allows for a maximum sperm life of five days (under ideal and very rare conditions) and ovulation day plus the following day.

There are two ways in which people discuss the time period related to milestones in fetal development: Gestational and fertilization age.

Fertilization age is a framework of time based upon the point of view of the unborn child, and begins at the instant of conception. The gestational (or menstrual) age timeline begins two weeks earlier at the last menstrual period, and is figured from the point of view of the mother. The framework most often used in discussions about the development of the unborn child is gestational age.

In other words, the normal convention holds that the 40 weeks of gestation begin in the first day of the last menstrual period, or two weeks prior to conception. A full-term baby is actually delivered 38 weeks after conception.

These terms can be somewhat confusing since they are based upon different starting points. Benchmarks of both are compared below.


                                                        Fetal                          Gestational
                                                  (Fertilization)                  (Menstrual)
                                                  Age in Weeks               Age in Weeks

Ovulation/fertilization                             0                                     2
Implantation                                          1                                     3
First missed menstrual period                 2                                     4
Preborn heart begins to beat                  3                                     5
Preborn brain waves begin                     6                                     8
All of preborn's body
   systems present                                  8                                   10
Birth                                                    38                                   40

Reference: Richard D. Glasow, Ph.D. "Clearing Up Confusion." National Right to Life News, July 30, 1991, page 11.

Postovulation infertility begins one or two days after ovulation. This phase, lasting until the first day of menstruation, is extremely infertile, much more so than during menstruation.

Some women experience pre-menstrual syndrome (PMS) before menstruation begins. This is a group of physical, mental, and behavioral symptoms that may include some or all of swelling breasts, clumsiness, irritability, fatigue, bloating, depression, and mood swings.

Other women may experience painful cramping, or dysmenorrhea. This is caused by contractions of the uterus during menstruation, which are in turn signalled by the secretion of prostaglandins.

The Hormonal Cycle.

The Beginning.

At the beginning of the cycle, shortly after menstruation begins, the pituitary gland, located near the base of the brain, secretes follicle-stimulating hormone (FSH). This hormone stimulates the growth and development of an ovarian follicle and its ovum. The follicle, after a certain period of time, begins to secrete increasing amounts of the hormone estrogen.[2]

Before Ovulation.

This hormone reaches a peak about a day before ovulation, and the pituitary gland then secretes another hormone known as luteinizing hormone (LH). The LH stimulates the follicle into releasing its egg, the process known as ovulation.

Upon being ejected, the egg faces a life span of from 15 to 24 hours unless it is fertilized. However, the follicle that is left behind is far from finished with its task. It even takes on a new name: The corpus luteum, or "yellow body." It performs several critical functions related to reproduction.

After Ovulation.

After ovulation, the corpus luteum secretes the hormone progesterone for about 10 days to two weeks. This hormone performs five functions. It maintains the lining of the uterus, prevents another ovulation from taking place, and triggers the three indicators used in the sympto-thermal method of natural family planning: (1) the basal (base) body temperature rises from 3/10 to 5/10 of a degree; (2) it causes the natural mucus in the cervix to thicken or disappear; and (3) it causes the cervix to rise and close.

After ovulation, the estrogen level falls sharply and then stabilizes until menstruation.

After 10 to 14 days, the corpus luteum ceases to secrete progesterone. This means that the uterine lining is no longer being maintained, and it breaks down and is sloughed off during the process of menstruation.

The time between ovulation and the beginning of menstruation is referred to as the luteal phase and is usually about two weeks long.

References: Human Reproduction.

[1] Mahatma Gandhi, quoted in Father A.S. Antonisamy. Wisdom for All Times: Mahatma Gandhi and Pope Paul VI on Birth Regulation. Family Life Service Centre, Archbishop's House, Pondicherry 605001 India. June 1978. Quotes are taken from D.G. Tendulkar (Editor). The Collected Works of Mahatma Gandhi, Volumes 2 and 4. Published by the Ministry of Information and Broadcasting, Government of India.

[2] Most of the material from this chapter is extracted from John and Sheila Kippley's book The Art of Natural Family Planning, which is the best available resource for explaining the human reproductive system and its functions in a manner that can be understood by the average person. The information is provided in a context of respect for God's gift of reproduction. In particular, the material in Chapter 5 of the Kippley's book, "The Basic Physiology of Human Reproduction," is very useful for those who wish to understand human reproduction. The third edition of this book may be ordered from the Couple to Couple League, Post Office Box 111184, Cincinnati, Ohio 45211-1184. The Couple to Couple League (CCL) has qualified over 1,000 couples all over the world to teach the safest, least expensive, and most morally acceptable form of birth control: natural family planning. If you are interested in learning this method, write to CCL, or call them at (513) 661-7612.

Further Reading: Human Reproduction.

The American College of Obstetricians and Gynecologists, Committee on Patient Education. Patient Information Pamphlet series. 
No. P-041, "Growing Up (April 1984)," and No. P-049, "Menstruation: and the Menstrual Cycle (March 1985)."

Couple to Couple League. "A Physician's Reference to Natural Family Planning." 
This pamphlet explains the reproductive system in greater detail, including the hypothalamic-pituitary relationship, threshold levels of pre-ovulatory estrogen, and the relationship between the ovaries.

Thomas W. Hilgers, M.D. Reproductive Anatomy and Physiology for the Natural Family Planning Practitioner
Creighton University Natural Family Planning Education and Research Center, 601 North 30th Street, Omaha, Nebraska 68131. 1981, 107 pages. Reviewed by John J. McCarthy, Jr., M.D., in the Fall 1983 issue of the International Review of Natural Family Planning, pages 272 and 273. This work fills a void for NFP instructors who have questions about human physiology and why the human reproductive system works the way it does.

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This is a chapter of the Pro-Life Activist’s Encyclopedia published by American Life League.