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Considering The Risks And Benefits Of The Birth Control Pill

From a message posted on Facebook:

Is the pill safe? The International Agency for Research on Cancer in a 2007 study made by 21 scientists reported that the pill causes cancer, giving it the highest level of carcinogenicity, the same as cigarettes and asbestos. It also causes stroke, and significantly increases the risk of heart attacks. Several scientific journals have stated that the natural way of regulating births through the Billings Ovulation Method has no side-effects, and is 99.5 % effective.

The Billings Ovulation Method (BOM) is a method of natural family planning where women are taught to recognize when they have ovulated by examining their cervical mucus, allowing them to avoid intercourse during fertile periods or conversely, to have intercourse during fertile periods when pregnancy is desired. We used to call people who used the rhythm method “parents,” but BOM is more reliable than older abstinence methods.

I’m a big fan of oral contraceptives. They contributed to women’s liberation by giving us a reliable method of planning, delaying, or avoiding pregnancy.  They also have medical uses that go beyond contraception. Birth control pills (BCPs) have had such an important impact that they are known as simply “The Pill.” We have always known they were not 100% risk free; but we also know they are less risky than pregnancy itself. There are other methods of birth control; but they are generally less effective and less convenient.  For those who want permanent solutions, tubal ligation and vasectomy are available; but even they have occasional failures. What does science tell us about the effectiveness and safety of BCPs as compared to other methods?

Effectiveness

According to the Wikipedia entry, the Billings Ovulation Method has a failure rate of 0-2.9% with perfect use and 1-5% with typical use.  (They cite the original references for these figures). The corresponding numbers Wikipedia gives for “the pill” are 0.3% and 8%. The American Congress of Obstetricians and Gynecologists’ numbers for the pill are a bit less optimistic: they say “With typical use, about 8 in 100 women (8%) will become pregnant during the first year of using this method. When used perfectly, 1 in 100 women will become pregnant during the first year.”

A handy table on the FamilyDoctor website compares the failure rates of various birth control methods. It lists periodic abstinence methods as having a 20% failure rate, but that includes the less effective rhythm methods as well as the methods based on mucus examination.

Cancer? It Causes Some Cancers and Prevents Others

Information on cancer and oral contraceptives can be found here.  There is an increased risk of cervical cancer, but most cases are related to HPV infection, so hopefully the new vaccines will eliminate much of that risk. There is an increased risk of liver cancer in low risk populations but not in high-risk populations. The risk of breast cancer may or may not be slightly increased: studies do not agree.

On the other hand, the pill clearly reduces the risk of uterine and ovarian cancers. And a meta-analysis found that the risk of colorectal cancer is also decreased.

The magnitude of these risks is small. I couldn’t find any information about overall cancer risk: whether the increase in some types of cancer outweighs the decrease in others.

What the IARC Really Said

According to the Facebook poster, the International Agency for Research on Cancer (IARC) said oral contraceptives were as carcinogenic as cigarettes and asbestos.  That’s not what the IARC said at all. It does classify estrogen/progesterone in the same group 1 category as cigarettes and asbestos, but all that category means is that there is sufficient evidence to prove carcinogenicity in humans. It does not in any way imply that oral contraceptives are as carcinogenic as cigarettes and asbestos: they aren’t.  And the IARC entry clearly states

There is also convincing evidence in humans that these agents confer a protective effect against cancer in the endometrium and ovary.

Other Risks

BCPs increase the risk of deep venous thromboembolism and ischemic stroke. There is disagreement over whether they increase the risk of myocardial infarction. The absolute risk of all these conditions is low. It is greater in smokers and in those with other risk factors, and it is lower for the newer low dose BCPs.

The ACOG has prepared an excellent patient education pamphlet listing all the risks, benefits, side effects, and contraindications.  It concludes:

The pill is a good choice for women who may want to get pregnant later. It is a safe and effective way to prevent pregnancy. It is easy to use, convenient, and reversible. The pill may protect against some cancers. Some benefits of pill use last months or years after you stop taking it. For almost all women, the benefits of pill use outweigh the risks.

Benefits

Critics of hormonal contraception fixate on the risks, but there are also a number of health benefits. The ACOG patient information pamphlet explains that BCPs reduce the risk of

  • Cancer of the uterus and ovary
  • Ovarian cysts
  • Pelvic infection
  • Bone loss
  • Benign breast disease
  • Symptoms of polycystic ovary syndrome
  • Anemia (iron poor blood)
  • Ectopic pregnancy
  • Acne

They also

  • Help to keep periods regular, lighter, and shorter and reduce menstrual cramps
  • Reduce symptoms of endometriosis and fibroids
  • May help with migraine headaches and depression.
  • Can be used to schedule periods to avoid an inconvenient time (i.e., a wedding).

Other Options

There are many other birth control options: condoms, diaphragms, other hormone delivery methods like cervical rings and injections, IUDs, spermicides, periodic abstinence methods, and therapeutic abortions. Some methods have the additional benefit of protection against sexually transmitted diseases. Some methods require specific actions at the time of intercourse, which some people object to as interfering with spontaneity. The periodic abstinence methods have the disadvantage of requiring periodic abstinence.

I remember reading years ago (the reference is long gone and I don’t know if the information is still valid) that when all factors were considered including the risks from pregnancy itself when contraception fails, the safest method of birth control was to use condoms and do therapeutic abortions when they failed. That resulted in statistically less morbidity and mortality overall than any other method. Of course there are other considerations that make this a less than ideal option. Emotions and religion create a lot of bias in the area of birth control. I suspect some people who reject oral contraceptives as “unsafe” might be quite willing to take other medications that have a similar safety profile but are not connected to ideological concerns.

Conclusion

BCPs are not risk-free, but the Facebook poster was wrong: their risks can’t be compared to the risks from cigarettes and asbestos. There are other good alternatives that some individuals may prefer for various medical and non-medical reasons. For any method of birth control, the risks must be weighed against the benefits. Pregnancy itself is far riskier than any method of pregnancy prevention.

The safest, most effective method of birth control is orange juice. You may ask “Before or after?” The answer is “Instead of.” Most women and their partners would not consider that a satisfactory option.

*This blog post was originally published at Science-Based Medicine*


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