The Pill: How Does it Work? Is it Safe?

Author: Couple to Couple League


Controversy has surrounded "the Pill" ever since it was first marketed in the United States in 1960. It has been studied medically, sociologically and morally, and yet much confusion still exists concerning these potent artificial steroids. The billions of dollars at stake in the marketing of the Pill and the power of the birth control industry to lobby both lawmakers and the media can easily divert the average person from the truth. Research has been published, books have been written, and common sense should make one cautious.

The following information is presented to raise awareness about the Pill. Footnotes are marked with astrisks; all footnotes appear at the end of this document in a section titled REFERENCES.


The Birth Control Pill is any drug which uses artificial hormones to keep a woman from getting pregnant or from staying pregnant by interfering with her normal fertility. Are all forms of the Pill the same?

No. There are several types of the Pill on the market, but they basically break down into two groups: combination pills and the progestin-only "minipill."

The combination type contain two artificial steroids that mimic the effects of naturally occurring hormones, estrogen and progesterone. Some pills work in a "monophasic" way, keeping the dosage of hormones the same throughout the pill cycle. Others work in a biphasic or triphasic manner which alters the dosage of artificial hormones two or three times respectively through the cycle of pills, attempting to produce fluctuations similar to what a fertile woman would undergo naturally.

The progestin-only "minipill" uses only one artificial hormone, progestin, which is a steroid that has a progestational effect similar to natural progesterone.


The Pill is designed to interfere with several normal functions of fertility in order to make a woman 1) unable to conceive due to temporary sterility or sperm immobility, and/or 2) unable to carry a pregnancy to term(an early abortion). This process can be accomplished in various ways.

1. Suppressing Ovulation: When a woman ovulates, hormones released from the pituitary , a gland located at the base of the brain, stimulate her ovaries to ripen and release an egg. The combination pill usually interrupts the release of these pituitary hormones resulting in no egg being released from the ovary, thus preventing pregnancy from occurring. With no egg available for fertilization, the woman is chemically sterile. The progestin-only pill, however, has a weaker effect. It generally does not suppress ovulation.[1]

2. Inhibiting Implantation: Another important aspect of fertility is the process by which the lining of the uterus is replenished and maintained. After an egg is fertilized, it normally implants in this lining (endometrium), drawing nourishment and sustenance. The progestin component of the combination pill and the progestin-only minipill cause the inner lining of the uterus to become thin and shriveled, unable to support implantation of the embryo(newly fertilized egg).[2]

3. Impeding Sperm Migration: Preceding ovulation, a woman's cervix produces a watery mucus through which sperm swim to meet the egg. The mucus also provides nourishment to sustain the life of the sperm cells. This mucus thickens under the influence of a progestin and so impedes sperm migration.[3]

There are two other factors in a woman's fertility that may be affected by the Pill.

4. Making changes in the Fallopian Tubes: Progestins lower the efficiency with which the fallopian tubes propel eggs from the ovaries toward the uterus. This can cause the embryo not to reach the uterus in time to implant successfully.[4]

5. Stopping a Pregnancy: After an ovary releases an egg, the woman's cycle is controlled by a gland that is formed from the now-empty egg sack, the corpus luteum; this normally functions long enough to give an embryo time to implant in the uterus and for the placenta to begin to support the pregnancy.

However, hormones from the Pill can cause the corpus luteum to function inadequately, allowing the lining of the uterus to be shed before the embryo can successfully implant.[5]

In summary, a woman's natural fertility requires several systems and organs to coordinate smoothly. The synthetic chemicals in any type of birth control Pill interfere with this coordination, adversely affecting her normal fertility and any "accidental" conceptions.


In theory, the Pill reaches an effectiveness of over 99%, but in practice the rate is much lower. Between 1.9% and 18.1% of women will experience an unplanned pregnancy in the first year of using the Pill.[6]

Surprise pregnancies with the Pill are due to a number of factors. Interactions between the Pill and some other medications interfere with the proper blood levels of hormones necessary for their birth control effect. These drug interactions may be significant with the commonly used "low dose" Pill where slight alterations in hormonal blood levels can result in more frequent ovulations and hence unplanned pregnancies. Another factor in Pill pregnancy rates is not following directions, sometimes due to the lack of motivation, especially in younger women (ages 15-24).


No. Ovulation occurs in 2% to 10% of cycles of women taking the Pill.[7][8][9][10][11][12][13] If 60 million women worldwide are on the low-dose Pill, there would be 1.2 to 6 million ovulations per cycle. This is known as breakthrough ovulation, and it is even more frequent with the progestin-only Pill.[14][15]


When the Pill fails to prevent ovulation, the other mechanisms come into play. Thickened cervical mucus may make it more difficult for the sperm to reach the egg; however, if the egg is fertilized, a new life is created. The hormones slow the transfer of the new life through the fallopian tube, and the embryo may become too old to be viable when it does enter the uterus. If the embryo is still viable when it reaches the uterus, under-development of the uterine lining caused by the Pill prevents implantation. The embryo dies and the remains are passed along in the next bleeding episode which, incidentally, is not a true menstruation even though it is usually perceived as such.


Yes. Preventing the newly conceived life in its embryonic stage from being transported to the uterus and preventing implantation in the wall of the uterus are the "abortifacient" properties of the Pill.


The Pill manufacturers and many in organized medicine are mainly concerned about the Pill's medical side effects and its effectiveness in preventing pregnancies and are less concerned about how the drug achieves its effectiveness.

Unfortunately, many "otherwise" pro-life physicians and pharmacists find it hard to admit that these abortifacient properties exist because they would have to discontinue prescribing and dispensing the Pill if they were to remain consistent in their respect for life at all its stages of development.

Pro-abortion organizations and their lawyers readily admit the early abortion potential of the Pill. In February 1992, writing in opposition to a Louisiana law banning abortion, Ruth Colker, a Tulane Law School professor, wrote, "Because nearly all birth control devices, except the diaphragm and condom, operate between the time of conception...and implantation.., the statute would appear to ban most contraceptives."[16] In 1989, attorney Frank Sussman argued before the U. S. Supreme Court that ". . . IUDs (and) low dose birth control pills. . . act as abortifacients."[17]


There is a range of risks from serious or fatal to minor and trivial. The following is a list of the most common side effects experienced by women taking the Pill. These effects are dose related and not every woman will experience them, but the risks still exist.[18][19] The synthetic estrogens of the combination Pill cause many of these; the progestin causes others and is the only risk factor in the progestin-only Pill (and the progestin-only implant, Norplant).


Blood Clots can form, restricting or blocking the flow of blood to critical organs and other body systems, possibly causing permanent damage. For example, a blood clot in the heart would cause a heart attack; in the brain it would cause a stroke or brain hemorrhage; a clot which moved from elsewhere in the body and lodged in the lung would cause a pulmonary embolism; in the kidneys a clot would cause a renal artery thrombosis and kidney damage; in the retinal arteries it would cause temporary or permanent blindness.

Studies continue to indicate approximately a 2-fold increased risk of fatal heart attacks among users of the current low-dose pill when compared to non-users.[20] This risk is lower than the risk experienced with the older high dosage pill, but it continues to be significant. Similarly, the risk of a fatal brain hemorrhage is increased 1.4 times when comparing users to non-users. Among women who smoke, there is a 12-fold increase in fatal heart attacks and a 3.1-fold increase in fatal brain hemorrhage.[21]

High Blood Pressure and alterations in the blood clotting mechanisms may be seen in women on the Pill.[22] This may contribute to a 3-11 times increased risk of developing blood clots in Pill users compared to non-users. The risk is especially great for women who smoke and/or are over 35 years old.[23]


Breast cancer has been repeatedly associated with using the Pill.[24][25][26][27][28][29][30][31]

Breast cancer has been increasing at an alarming rate in recent years, especially among young women. "Breast cancer will kill more than 44,000 American women this year alone," a 1991 report noted,[32] predicting 175,000 more new cases, "especially among young women."

Why is there such an increase of breast cancer among younger women? Note first that women rarely develop breast cancer shortly after they start taking artificial hormones. It is generally not until ten or more years after usage was initiated that women develop breast cancer. Then note that in the United States, since the mid-1970s, it has been common for the Pill to be prescribed for girls in their teen years. Common sense connects the link between giving the Pill to young girls in the 1970s and the later increase in breast cancer 15 to 20 years later among women in their late twenties and thirties. This conclusion was demonstrated in a study which found that Swedish women who took the Pill in the 1960s incurred a five times greater increase in breast cancer when compared to non-users.[33]

The increased risk of breast cancer is seen in younger, nulliparous women (never having borne children), and in long duration groups (greater than five years) of Pill users. Large tumors and a worse survival rate are associated with the Pill's use at an early age.

Will the newer formulated low-dose pills decrease the incidence of breast cancer? A consensus of understanding has not been reached, and another 10 to 20 years of experience with women using this form of the Pill must be gained before more definite conclusions can be reached.

Breast tenderness, enlargement, lumps, and milk secretions also may occur in women using the Pill. Doctors are warned not to prescribe the Pill to women who are "known or suspected" to have breast cancer.[34] It is difficult to say what aggravating effect the Pill's hormones would have over a truly random sample of women taking the Pill.

Cervical Cancer and cervical dysplasia increase among women who use the Pill.[35][36][37][38][39] How long the Pill has been taken, how many sexual partners a woman has had, at what age she began having intercourse, whether she smokes, the hygiene of sexual partners and the transmission of the human papillomavirus(HPV) are also factors in cervical abnormalities. Because of these several factors, the connection of the Pill and cervical cancer may be clouded over. However, there is no doubt that the promotion of the Pill has resulted in early intercourse which may be the more direct cause of cervical cancer.

Endometrial and Ovarian Cancer appear to have a lower incidence in both women on the Pill and in those who have been previous users of the Pill. Much of this data comes from studies of women who were using the higher dose estrogen/progestin Pill. Currently the low dose monophasic and triphasic pills (less than 50mcg of estrogen) are the only birth control pills available on the U.S. market. It is not known if a similar protective effect will be experienced with the currently used Pill. More time is needed to study this issue, and the slight protective effect is hardly a reason to take the Pill at the risk of so many other side effects.

It should also be noted that these forms of cancer are rare and primarily occur among postmenopausal women in their fifties and sixties. Second, these cancers tend to occur in those women who had long cycles (i.e., with a prolonged estrogen-dominant phase) or those who have a family history of these types of cancer. Third, extended breastfeeding amenorrhea offers the same type of protection against these cancers since the menstrual cycle would be suppressed and therefore the exposure to estrogen suppressed.

Liver Tumors in younger women (15 to 40 years) have increased as the use of oral contraceptives has increased. Almost unheard of in this age group before the use of synthetic hormones became commonplace, liver tumors usually do not occur until the sixth decade of a woman's life.

A study by the American College of Surgeons' Commission on Cancer found "a large peak in the 26-to-30-year age group which corresponds with the increased use of oral contraceptives in this age group."[40] Liver cancer in women on the Pill is typically associated with those over 30 who have used it more than four years, but cases of liver cancer in younger women have been cited.[41][42][43][44]

Other Cancers: Skin cancer (melanoma) has also been found to increase among women on the Pill. Naturally occurring estrogen is involved with maintaining healthy skin tissue. It is reasonable to suspect that exposure to the more potent synthetic estrogen in the Pill increases the risk of this type of cancer.[45][46][47]


Women who take the Pill have been reported to experience bleeding or spotting in mid- cycle, changes in menstrual flow, and even loss of menstruation, which can lead them to wonder if they are pregnant. For some, painful menstruation (dysmenorrhea) has been reported to worsen, even though many women take these hormones in an attempt to relieve the problem.[48]

Although some women are given the Pill for irregular cycles, it does nothing to improve the underlying problem causing the irregularity. Often the irregularity returns when the Pill is discontinued, sometimes more severely.


Yes. Some side effects are minor while some may be more severe and call for discontinuing the drug.[49][50][51]

The following adverse effects have been experienced by women on the Pill:

Headaches, migraines, mental depression (even to the point of suicide and/or suicidal tendencies), a decrease or loss of sexual drive, abdominal cramps, bloating, weight gain or loss, and water retention; nausea and vomiting(in about 10% of users); symptoms of PMS, vaginitis and vaginal infections, changes in vision (temporary or permanent blindness, and an intolerance to contact lenses); gall bladder disease and either temporary or permanent infertility, when discontinuing the Pill, in users with previous menstrual irregularities or who began the drug before full maturity. Several of the symptoms, such as migraine headaches, contraindicate the use of the Pill because of life endangering complications.

Consult the Physicians' Desk Reference at your public library or consult your pharmacist for a more complete list of the Pill's harmful effects.


No. The health risks of the Pill outweigh by far the risks of pregnancy and childbirth to a woman's health,[52] and any claim to the contrary is based on erroneous comparisons between healthy women on the Pill and women who do not receive normal care during pregnancy.

A precondition for obtaining the Pill is routine medical care and checkups. For example: if such a woman on the Pill is diagnosed as "precancerous," or if some other side effect is exhibited, she has the advantage of early detection. However, many pregnant women do not receive routine medical care. A clearer picture of the safety of the Pill compared to the safety of pregnancy would be made if healthy women receiving routine medical care during pregnancy and delivery were compared with women receiving routine medical care while taking the Pill.

The mortality statistics of childbirth have continuously declined since the early part of this century, mostly due to better maternal healthcare.[53] Most of the high risk pregnancies and deliveries occur to women who have not sought proper medical attention.[54] This is most evident in the Third World where adequate health care is sparse.

Mortality statistics of pregnancy and delivery, usually called maternal mortality, include the mortality rates due to abortion. Abortion is clearly used as birth control, preventing the birth of the child; therefore it must be included with the mortality statistics of birth control methods. In one study, 25% to 50% of the reported maternal mortality was a result of deaths from abortion.[55]

Fifty percent of woman taking the Pill discontinue it within the first year because of side effects, the development of benign breast disease, or some abnormality of the sexual organs. Studies of Pill usage do not include these women, and the result is an unbalanced picture of only the healthiest of women who tolerate the Pill.[56] This is compared with the general population of women who are pregnant.

The fact is that there are 13.8 million women in the U.S. and 60 million women worldwide who use the Pill (conservative numbers).[57] And there are 7.9 Pill-related deaths per 100,000 women ages 15-44.[58]

Therefore, one can calculate that there are over 1090 deaths each year in the U.S. alone simply due to the Pill.

But I've heard there are no side effects with the Pill I use.

All drugs, including all brands of the birth control pill, have potential side effects. There is no telling in advance how any particular woman will react to the Pill, but there is a good chance of some type of reaction. It is possible that a woman will be unaware that there is any connection between the reaction and the Pill especially if it takes years to manifest itself.


The only "indication," or use for the Pill that is approved by the Food and Drug Administration is "the prevention of pregnancy in women . . . as a method of contraception."[59] Some unapproved uses, considered experimental, include its use as a "morning after" pill (causing an early abortion), and for relief from the symptoms of mild endometriosis.[60]


No. Artificial hormones pass from breast milk to the baby; the Pill also decreases both the quantity and protein content of the milk produced.[61]


Natural Family Planning (NFP) is safe, healthy and effective and it's also inexpensive. A woman observes and records changes in her basal body temperature, the normal flow of cervical mucus, and if she wishes, the physical changes in the cervix itself. She then crosschecks these signs of fertility to follow, day by day, the natural course of her fertility cycle. No drugs, no devices, no surgical procedures, no threat of death, no side effects, no chemical abortions!


Yes. Married couples can achieve a 99% effectiveness if they learn the method, correctly interpret the fertility signs, and follow the rules.[62] One positive side benefit for couples who are committed to making this method work is the potential for a healthier marriage -- psychologically, physically and spiritually.[63][64]

-- Paul Weckenbrock, R.Ph.

How can I find out more about Natural Family Planning?

Write the national office of The Couple to Couple League, P. O. Box 111184, Cincinnati, OH 45211; (513) 661-7612.


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61. Oral Contraceptives (Nov 1989 insert). Facts and Comparisons. 107g.

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63. Kippley, J Kippley, S (1991). The Art of Natural Family Planning. (3rd ed, 5th print) Cincinnati: Couple to Couple League 59-74.

64. Tortorici, J (1979). Conception regulation, self-esteem, marital satisfaction among Catholic couples: Michigan State University study. Int Rev NFP III(3) 191-205. ---------------------------------------------------------------------------- c 1993 The Couple to Couple League International, Inc. P.O. Box 111184, Cincinnati, OH 45211-1184, USA. (513) 661-7612

This information is from a brochure titled "The Pill: How does it Work? Is it Safe?" The brochure and related material may be ordered from Couple to Couple League direct or through CRNET's Catholic MarketPlace.