Breast Cancer Risk from The Pill

Chris Kahlenborn
Reproduced with Permission
One More Soul

How could the Pill cause breast cancer?

Two of the most important types of hormones that control reproduction are estrogens and progestins. Birth Control Pills are made from synthetic estrogens and/or progestins. Experiments have shown that these hormones cause women's breast cells to divide more rapidly, which makes them more easily affected by carcinogens - agents which cause cancer.

Has this been proven?

Yes. Eighteen of the twenty-one research studies done since 1980 on the connection between the Birth Control Pill and breast cancer showed that Pill users have a higher risk of breast cancer than non-users. An analysis in 1990 of the research up to that time1 showed that women who used the Pill for 4 or more years before their first full-term pregnancy had a 72% increased risk of developing breast cancer.

What does it mean to have "a 72% increased risk of developing breast cancer?"

A 72% increased risk means a 72% higher risk than someone would otherwise have. For example, if a person had a 10% risk of developing breast cancer, then a 72% increase would bring the risk up to 17.2%.

How serious a problem is breast cancer?

Breast cancer is the worldwide leading cancer in women and is the most common cause of cancer death in U.S. women age 20-59. In the U.S. every year about 175,000 women are diagnosed with breast cancer and more than 43,000 women die from this disease2. This means that about one U.S. woman out of eight will develop breast cancer at some time in her life and one fourth of such women will die from this disease. Using the Birth Control Pill, especially at a young age, markedly increases a woman's risk for developing breast cancer. This risk is increased even higher when combined with other breast cancer risk factors such as induced abortion, hormone treatment (such as estrogen supplementation), family history of breast cancer, and other factors.

The U.S. has one of the highest rates of hormonal contraceptive use (73% to 90% of women born after 19503,4) and induced abortion in the world, especially in young women (eg 44 abortions per thousand women under 19 compared with at most 30 per thousand for any other country5).

Are some groups of women in greater danger?

Yes. The research shows that the Birth Control Pill increases the risk of breast cancer more for some groups of women than for others. Groups at especially high risk include younger women, women who have not given birth, women who have a family history of breast cancer, those who took Birth Control Pills for long periods (four years or more), and young black women.

Why would black women have more breast cancer?

Breast cancer in the U.S. is more prevalent in young black women than in white women of equivalent age (eg 45.6 compared to 40.3 new cases per year per 100,000 women6), and is the second leading cause of cancer death (after lung cancer) among black women. This may be a consequence of more common hormonal contraceptive use and/or a greater frequency of abortion among young black women. Black women who develop breast cancer generally have more aggressive cancers resulting in a shortened life expectancy.

What is the risk for young women?

Studies of women who used oral contraceptives at an early age indicate that when they develop breast cancer they tend to have larger tumors, more aggressive tumors, greater prevalence of metastatic cancer, and a shorter life expectancy.7

What if there has been breast cancer in my family?

Women who have a family history of breast cancer and use oral contraceptive pills have an increased risk from both factors. For example, if a woman's mother or sister has had breast cancer, her risks from other factors such as abortion and/or oral contraceptives are increased.

Do some contraceptives cause more risk than others?

Yes. Research studies show that breast cancer risk is almost tripled for women who used Depo-Provera for 2 years or more before age 25.8 Norplant, which uses the same type of chemical as Depo-Provera, may carry a similar risk.

Are other types of cancer affected by oral contraceptive pills?

Oral contraceptive pills decrease the risk of uterine and ovarian cancer, but increase the risk of breast, cervical and liver cancer. It is estimated that an additional 40,000 - 80,000 cases of cancer will occur in the U.S. annually when the effect of oral contraceptives on all types of cancer is considered.

Aren't there other risks from contraceptives?

Certainly. Well known side effects of the Pill include an increased frequency of blood clots, high blood pressure, and heart attacks, as well as migraines, depression, loss of libido, and a variety of other disorders. Less well known is that oral contraceptives and injectable progestins (such as Depo-Provera) significantly increase the risk of contracting and transmitting HIV (the AIDS virus).9,10 In addition, today's oral contraceptives work, at times, by causing an early abortion.11

How can I protect myself?

Many of the known risk factors for breast cancer can be avoided: hormone exposure (including hormonal contraceptives), abortion, heavy alcohol use, obesity, and radiation exposure. In addition, there is a significant reduction of risk with each child a woman bears. Every month of breastfeeding reduces breast cancer risk, as does bearing a child at a younger age. Vitamin A (which should not be taken in high doses by women who could become pregnant) and some "anti-estrogen" medications may offer some protection. Any woman, especially if she has one or more of the known risk factors, should consult a physician regularly and perform frequent self-breast exams.

If hormonal contraceptives and abortion are so dangerous, what options do couples have?

Natural Family Planning (NFP) methods are available which use no chemicals or surgery and cause no increase in breast cancer risk. Not to be confused with the "rhythm method," NFP is based on observations of a woman's cervical mucus and (for some methods) other symptoms as well. One of the largest research studies of NFP (involving 19,843 women and performed in India by the World Health Organization) showed a pregnancy rate of 0.2 pregnancies per 100 women yearly.12

Natural Family Planning methods have been used to diagnose and treat a variety of female reproductive disorders including infertility. Various medical problems (eg. excessive menstrual cramping and bleeding) can be treated far more safely with less toxic means (eg. magnesium/calcium supplements and/or ibuprofen products).

How can I find out more about breast cancer risk from the Pill?

The book Breast Cancer, Its Link to Abortion and the Birth Control Pill by Chris Kahlenborn, MD, is available from One More Soul. Eleven of the seventeen chapters in this book deal with cancer risks from Birth Control Pills. It contains an extensive bibliography of over 500 references on this and related topics. The material in this pamphlet is based upon information from Dr. Kahlenborn's book.

Where can I find information about natural family planning?

Natural family planning information is available from a number of national organizations:

Billings Ovulation Method Association
(888) 637-6371

Couple to Couple League
(513) 471-2000

Family of the Americas
(800) 443-3395

National Conference of Catholic Bishops
(202) 541-3240

Northwest Family Services
(503) 215-6377

One More Soul
(800) 307-7685

Pope Paul VI Institute
(402) 390-6600

St. Augustine Foundation
(877) 554-4637

Many Catholic dioceses have NFP offices or family life offices which can supply NFP information. Local parishes and Catholic hospitals may also be good sources.


1 Romieu I, Berlin J, et al. Oral contraceptives and breast cancer, Review and meta-analysis. Cancer. 1990; 66: 2253-2263. [Back]

2 Landis SH et al. Cancer Statistics, 1999. CA Cancer J Clin. 1999; 49: 12-23. [Back]

3 Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and hormonal contraceptives: further results. Contraception. 1996; 34: S1-S106. [Back]

4 Brinton LA, Daling JR et al. Oral contraceptives and breast cancer risk. J Natl Cancer Inst. 6/7/95 87: 827-835 [Back]

5 Tietze C. Induced Abortion: A World Review. 5th ed. Population Council; 1983. [Back]

6 National Cancer Institute. SEER Cancer Statistics Review. 1973-1992: Tables and Graphs. Bethesda, Maryland. [Back]

7 Olsson H, Ranstam J, et al. Proliferation and DNA ploidy in malignant breast tumors in relation to early contraceptive use and early abortions. Cancer. 1991; 11: 2043-2046. [Back]

8 Skegg DCG, Noonan EA, et al. Depot medroxyprogesterone acetate and breast cancer [A pooled analysis of the World Health Organization and New Zealand studies]. JAMA. 1995:799-804. [Back]

9 Ungchusak et al. Determinants of HIV infection among female commercial sex workers in northern Thailand: results from a longitudinal study. J Ac Immune Defic Syn Hum Retro. 1996. 12: 500-507. [Back]

10 Mostad SB et al. Hormonal contraception, vitamin A deficiency and other risk factors for shedding HIV-1 infected cells from the cervix and the vagina. The Lancet 1997. 350: 922-927 [Back]

11 Larimore WL, Stanford J. Postfertilization effects of oral contraceptives and their relationship to informed consent. Arch Fam Med. 9; 2000: 126-133 [Back]

12 Ryder RE. "Natural Family Planning": Effective birth control supported by the Catholic Church. Br Med J. 1993; 307: 723-726. [Back]

Dr. Chris Kahlenborn is an internist in private practice in Altoona, PA. Dr. Kahlenborn is the author of Breast Cancer, Its Link to Abortion and the Birth Control Pill.