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Birth Control Fails More Often Than People Realize

posted on January 8, 2020 by Jessica Davidson Jessica Davidson

Many medical professionals tend to look with skepticism at the effectiveness rates of Fertility Awareness-Based Methods (FABM) to prevent pregnancy, despite the research to back them up. As I was told at my six-week after birth followup by my OB-GYN: “you do know you can get pregnant on that [FABM]?”

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After my first baby, I was confident in our decision to use the Sympto-Thermal Method for natural family planning, but still wasn’t ready to correct my doctor’s underlying assumption that I would only be “safe” from an unexpected pregnancy if I used contraception. I blithely dismissed her concerns with a defense of how it’s possible to navigate postpartum with extra attention to the particular FABM’s guidelines (which is true). But I could have simply pointed out how someone can also get pregnant when they are using any form of contraception.

Does Contraception Really Work?

Initially, this seems an absurd question to ask in our modern era. The assumption that we have an abundance of effective contraceptive options undergirds any and all discussions of reproductive health, both domestically and internationally. An individual’s ability to access contraceptives may be in question, but not their existence. 

However, if you would humor me, I’d like to look at this question from two different angles: first, does contraception effectively reduce births on a societal level? Second, does it effectively prevent pregnancy on an individual basis? Then, let’s discuss why it’s beneficial for couples who choose a Fertility Awareness-Based Method, an evidence-based method of natural family planning (NFP), instead of a hormonal contraceptive method or device, to understand the answers to both of these questions.

How do researchers determine birth control effectiveness rates?

I once made the claim, during a discussion on Facebook about the effectiveness of contraceptives, I made the claim that all birth control methods have the potential to fail. This claim was hotly contested, even outright denied. One participant candidly shared that she had been using hormonal contraceptives for ten years and had never gotten pregnant; therefore, she was the obvious exception to my assertion. I soon left the discussion when I realized we were talking past one another. But I have never forgotten it, as it highlighted to me a few misconceptions many people have of how a contraceptive’s effectiveness is evaluated.

For a pharmaceutical or medical-device company to market a contraceptive, they must have effectiveness studies showing that in the study population of healthy, sexually active women the natural birth rate was reduced as close to zero as possible. In a healthy population of sexually active couples who are not trying to prevent pregnancy (so-called “unprotected sex”), and who are also not targeting their intercourse to fertile times of their cycle (so-called “random sex”), about 85% will be pregnant in a given year. That is, if there were 1000 couples having random, unprotected sex in a given community, researchers would expect about 850 of them to get pregnant within the year.

When a potential new contraceptive is being investigated, the researchers are seeking to determine the answer to this question: over the course of one year of using this drug or device, how many of the sexually active study participants conceived a child? They will record how many women began the study, used the drug/device for the entire time, and if they conceived (as well as other pertinent data). They will also note if the women who conceived were using the drug/device according to the correct protocol. From there, researchers calculate a method-effectiveness or “perfect use” effectiveness rate (when the correct protocol was used) and a “typical use” effectiveness rate (when correct protocol was not followed). These are the rates one will see on posters and websites.

These studies are accurate, but they reflect the use of the contraceptive on a particular population as a whole. The Pill, according to its effectiveness studies, has a method effectiveness greater than 99%, which means that for every 100 women who took the Pill exactly as instructed for the entire year, researchers saw no more than 1 woman get pregnant.

So to answer the first question above—does contraception effectively reduce births on a societal level?—yes, we as a society have a way to effectively reduce the number of overall births among sexually active couples, from 85/100 down to 1/100. But when we look at the second question—does it effectively prevent pregnancy on an individual basis?—the answer is: sometimes

In the Pill example above, for 99 of the 100 women in that scenario, the Pill 100% prevented pregnancy. But for the 1 woman, it 100% failed her. She’s left wondering, what went wrong? She did everything correctly and yet she is still pregnant when she did not plan to be. Looking at more realistic usage accounting for human error (the typical-use rate), the effectiveness of the Pill stands closer to 93%, which means that 7 out of 100 women using the Pill in a given year find themselves pregnant (1). For these women, the contraceptive failed.

Understanding how pregnancy happens

One aspect that differentiates a FABM from a contraceptive method of family planning is that using a science-backed method of natural family planning equips a woman to truly understand how her body works and to begin to see how her body is biologically geared toward conception during her reproductive years. It allows her to understand the way she functions and appreciate what her body is capable of, including pregnancy. Mastering a Fertility Awareness-Based Method gives every woman the ability to see her reproductive system as an integral part of her health and cooperate with this knowledge of her fertility to postpone pregnancy when needed, while recognizing that she will never be able to thwart or suppress her reproductive capacity entirely (prior to its natural conclusion at menopause) unless she removed her uterus.

At the same time, when we look at the effectiveness studies done for Fertility Awareness-Based Methods, we discover that the pregnancy prevention rates (both typical use and perfect use, depending on the method) are on par with contraceptive drugs and devices on the market, without suppressing or intruding upon a woman’s fertility cycle. So we can be confident that we aren’t foolish to rely on one of the modern fertility awareness methods even while we recognize that, just as with other birth control methods, effectiveness rates are based on averages for a group, not an individual couple’s likelihood of conceiving. That means some couples correctly using a FABM to avoid pregnancy will conceive a child. FABM users can increase the likelihood of their method working effectively by learning the method from a trained FABM instructor, being diligent in their charting and following the rules of their method for postponing pregnancy, and by checking back with their instructor when new or unusual charting patterns emerge.

It has been years since my OB-GYN reminded me I could get pregnant while using a Fertility Awareness-Based Method. Now, years later and after having learned more about the science behind fertility awareness and becoming a FABM instructor myself, I am more confident in my understanding of how FABMs effectively prevent pregnancy. I also have grown stronger in my understanding of how a healthy woman’s body allows all of her bodily systems to thrive at optimal wellness.


1. Trussell J, Aiken ARA, Micks E, Guthrie KA. Efficacy, safety, and personal considerations. In: Hatcher RA, Nelson AL, Trussell J, Cwiak C, Cason P, Policar MS, Edelman A, Aiken ARA, Marrazzo J, Kowal D, eds. Contraceptive technology. 21st ed. New York, NY: Ayer Company Publishers, Inc., 2018

Posted by Jessica Davidson Jessica Davidson
Jessica Davidson is a speaker for Fertility Appreciation Collaborative to Teach the Science (FACTS) and teaches the SymptoThermal method for the Couple to Couple League with her husband. She has a Masters of Theological Studies from the Washington DC session of the Pontifical John Paul II Institute on Marriage and Family Studies.