Actual Birth Control Failure Rates

Birth control is not as good as most people think in preventing accidental pregnancies. You may be familiar with numbers quoting failure rates in “perfect” use. But how many users are “perfect”?

Let’s take condoms as an example. Condoms are reported to have perfect use failure rates of 1-2%. But how many condoms were always stored perfectly? Have you ever left them in the car? In your wallet? At the bottom of a messy purse? How long did they sit in a hot warehouse before being delivered to your local drugstore? How many people know exactly how and when to use a condom? How many have a perfect fit? How many vaginas19 are frictionless? How many use the perfect lubricant? Or any lubricant at all?

You can see that there are a lot of ways imperfections can creep in—and they do as reflected by the 13% failure rate.

Even if condom usage is “perfect,” one or two girls in a hundred will still get pregnant in the first year of using condoms.

So let’s look at the actual failure rates of the various forms of birth control, starting from the least effective to the most effective.20

Method Actual Failure Rate
(number of pregnancies in first year)
None 85%
Spermicide 28%
Fertility Awareness 24%
Withdrawal 20%21
Female Condom 21%
Male Condom 13%22
Diaphragm/Sponge 12%
Pill/patch/ring 9%
Injectable 6%
Implant less than 1%
IUD 0.2-0.8%
Tubal ligation 0.5%
Vasectomy 0.15%

If you don’t use any method of birth control, there is an 85% chance of getting pregnant in the first year.

Spermicides are chemicals that kill sperm. They are inserted into the vagina before intercourse23 to prevent pregnancy. Spermicide is typically available as a foam or jelly, although other forms are available. While it can be used alone, you can see from the 28% failure rate that it isn’t very effective by itself. In fact, spermicides are intended to be used with barrier methods of birth control, such as the condom, diaphragm, sponge or ring.

Fertility awareness methods are a form of family planning that relies on tracking one’s periods and ovulation24 in various ways and not having sex at those times when it is possible to get pregnant. This method is inexpensive and doesn’t have any side effects. Some women choose to use fertility awareness methods for religious reasons. For example, the Catholic Church approves of various fertility awareness methods.

However, using the rhythm method for birth control requires careful record keeping, diligence and your periods must be regular. As chart above shows, it’s not very reliable with a 24% failure rate.

We will provide a whole chapter on using this method and each of the other methods later, so let’s move on.

Withdrawal means that the male pulls out of the vagina before ejaculation,25 and it’s not very effective (20% failure rate) by itself either. It is, however, free and has no side effects—if you don’t count pregnancy or disease!

Male and female condoms have a couple of benefits, namely that they are easy to buy and no prescription is needed. They also protect against both disease and pregnancy, and these are the only methods that do. However, used alone, they are not very reliable, failing 13-21% of users within the first year.

The diaphragm and the sponge are similar to the condom in that they are barrier methods of birth control—physically blocking sperm from reaching an egg, instead of relying on hormones to change egg production.

The sponge is a round piece of white plastic foam that is inserted into the vagina before sex, and left in afterwards for 6 hours. The sponge works in two ways: It blocks the cervix26 to keep sperm from getting into the uterus,27 and it continuously releases spermicide.

The diaphragm is a Frisbee shaped rubber cap that fits over the cervix. It is coated with spermicide, and inserted into the vagina before sex, and not removed for 6 hours after sex.

The failure rate is pretty high—12% for both of these barrier methods.

The pill, the patch and the ring are all hormonal methods of birth control. These act by changing the body in various ways. For example, some prevent eggs from being released from the ovaries,28 others thicken cervical mucus to prevent sperm from entering the uterus, and others thin the lining of the uterus to prevent implantation.29 The pill is taken every day, the patch is weekly, and the ring is inserted into the vagina every month. These each have about a 9% failure rate.

Hormones may have some negative side effects, but they can also have significant positive side effects. In fact, many women take some kind of hormone to regulate their periods and reduce the monthly discomfort. There are also many different kinds of hormonal regimes, and some trial and error may be needed to find one that is suitable for a woman.

The injection is also hormone based, and is taken every three months. There is a 6% failure rate for this method. However, one has to go to the clinic every three months to get the shot.

The implant releases hormones from a slender rod inserted under the skin of the arm. It lasts for 3 years, and because no action is required by the user, it is more effective than other methods. Although the CDC30 reports a 0.05% failure rate, that is not accurate, and many women have complained of unintended pregnancy while using the implant.31 The manufacturer suggests that when correctly inserted, the failure rate is less than 1%, and that is the number we have used in our chart.32

The IUD or “intra-uterine device” comes in two basic forms-one with hormones and one without. It is inserted into the uterus, leaving small strings protruding into the vaginal canal. The hormonal kind lasts 3-5 years and the non-hormonal can last 10-12 years.

The IUD is usually accompanied with some pain on initial insertion, heavier periods for 1-3 months, and it can be expelled, which is also painful. If your body accepts it, it can be nice to have years of fairly reliable birth control. The failure rate is less than 1%.

The failure rate of the two types of sterilization procedures is also less than 1%. In vasectomies, the vas deferens33 is cut or tied, and it is usually outpatient surgery, taking about 20 minutes, and the man usually takes a couple of days off work.

Tubal ligation34 for a women is a surgical method, involving anesthesia. Recovery times vary from 1-2 days to a few weeks. However, a new non-surgical method has recently become available to women.

Sterilizations are generally not reversible, and thus may be appropriate for an older person who already has a family. However, sterilization is also used for medical reasons where pregnancy might be dangerous to a woman’s health, or where a couple have hereditary problems they do not want to pass on to their children.

Some of you might be surprised that even sterilizations sometimes fail—they do. No method is foolproof. We will delve more into the reasons why in Chapter 8 on Sterilization.

You may have noticed that the failure rate of abstinence is conspicuously absent from our chart. That is because no one has done any research on the topic. Of course, the theoretical use is close to perfect. If you are on a desert island with no other human being present, it may be biologically impossible to get pregnant. However, we are dealing with facts here—not theory. Common sense suggests that in the real world, abstinence as a contraceptive method can and does fail.

For one thing, abstinence is difficult. The sex drive is at its highest when we are young, and it’s hard to say no. It can be especially hard when a woman is ovulating because that’s when she is at her most attractive to men.35

In addition, abstinence can’t work in the event of rape, nor can abstinence from penile-vaginal sex prevent STDs where oral sex and other forms of skin-to-skin contact are occurring. Even if you believe in the power of abstinence-only teaching, remember, teens don’t always get a choice.36

In summary, no method of birth control is perfect, and the very best methods have failure rates of less than 1%. That’s still one pregnancy in every hundred or so within the first year of use, and is something to remember as you consider whether or not to initiate sex in your relationship. Pregnancy is always a risk—married or not.

Further, we only discussed pregnancy as one possible consequence of the failure of birth control. Disease is actually a much bigger risk, given that there are 20 million new STD cases in the US every year37 and only 4 million births.38

In the next chapters, we will look at each of these methods more closely, providing instruction on their correct usage, most common reasons for failure, and suggesting ways to treble-up your protection.

If you want to compare the various methods side by side, https://www.bedsider.org/methods has a very convenient graphic that highlights key points as you pass your cursor over each method, and also groups methods by feature, such as “most effective” or “hormone free.” Additionally, this site is also available in Spanish.

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Endnote 19

Vagina — the canal leading from the uterus to the external genitalia in female mammals. A glossary at the back of this book provides more information on many terms used in this booklet. If you read it on a Kindle, that device will also provide definitions for any word you highlight.

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Endnote 20

Data from the CDC chart available online at https://www.cdc.gov/reproductivehealth/contraception/unintendedpregnancy/pdf/family-planning-methods-2014.pdf, except as noted herein.

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Endnote 21

Although the CDC website reports an 22% failure rate for withdrawal, the latest research shows there has been a modest improvement to 20%. Sundaram, A., et al., Contraceptive Failure in the United States: Estimates from the 2006–2010 National Survey of Family Growth, PERSPECTIVES ON SEXUAL AND REPRODUCTIVE HEALTH, 49(1): 7-16 (2017), available online at https://www.guttmacher.org/journals/psrh/2017/02/contraceptive-failure-united-states-estimates-2006-2010-national-survey-family.

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Endnote 22

The CDC reports an 18% failure rate for the male condom, but Sundaram (2017) reports some improvement to 13%. There has also been a small decline in failure rates for combined hormonal methods, but since these are not broken out by type, we have not used those numbers.

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Endnote 23

Intercourse is sex; here we are referring to penile-vaginal sex.

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Endnote 24

“Ovulation” is the release of an egg (ova) from the ovary (the female organ where eggs are made).

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Endnote 25

Ejaculation is the ejection of semen from the penis at orgasm.

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Endnote 26

The cervix is the lower part of the uterus, which can be reached inside the vagina.

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Endnote 27

The uterus is the female organ where babies grow and develop.

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Endnote 28

Ovaries are the organs that make eggs in the female body. The analogous organs in the male are the testicles, also called testes.

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Endnote 29

Implantation is the attachment of the fertilized egg to the wall of the uterus at the start of pregnancy.

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Endnote 31

Trussell, J., Contraceptive failure in the United States, Contraception, 83(5): 397–404 (2011), available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3638209/ (“Not one of 15 clinical studies has reported an Implanon failure. However, pregnancies during use of Implanon have been reported. We arbitrarily set the perfect-use and typical-use failure rates for Implanon at 0.05%.”) (cites omitted, emphasis added). To obtain accurate failure rates of birth control methods of less than 1%, the studies have to be of larger size.

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Endnote 32

Implanon: 600 pregnancies despite contraceptive implant, BBC News (2011), available online at http://www.bbc.com/news/health-12117299 (“The implant maker, MSD, said no contraceptive was 100% effective. It added that unwanted pregnancies may occur if the implant was not correctly inserted, and said it had a failure rate of less than 1% if inserted correctly.”).

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Endnote 30

CDC is the Center for Disease Control.

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Endnote 33

The vas deferens is a small tube that carries sperm from the testis, where sperm is made, to the urethra for ejaculation.

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Endnote 34

In tubal ligation, the fallopian tubes are cut. The fallopian tubes are the female analog to the vas deferens, carrying eggs from the ovaries to the uterus.

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Endnote 35

Abbasi J., Fertile Gals Look & Sound More Attractive: Study, Live Science (2010), available online at http://www.livescience.com/25457-fertile-women-attractiveness.html (“Men find women more attractive near ovulation, when they’re most fertile, suggests the largest study yet to look at whether a gal’s allure changes over the course of her menstrual cycle.”).

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Endnote 36

See https://www.rainn.org/statistics/victims-sexual-violence reporting that 1 in 6 women is the victim of attempted or completed rape over her lifetime, and that 1 in 10 rape victims is male. Female college students are 3 times more likely than women in general to experience sexual violence, and male college students are 5X more likely than men in general to experience sexual violence. Prison is also a very dangerous environment, as is the military. These numbers suggest that even if abstinence is your plan, that a long acting reversible birth control (“LARC”) method may still be a good backup plan.

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Endnote 37

Reported Cases of Sexually Transmitted Diseases on the Rise, Some at Alarming Rate, 2015, CDC, available online at https://www.cdc.gov/nchhstp/newsroom/2015/std-surveillance-report-press-release.html (“Despite being a relatively small portion of the sexually active population, young people between the ages of 15 and 24 accounted for the highest rates of chlamydia and gonorrhea in 2014 and almost two thirds of all reported cases. Additionally, previous estimates suggest that young people in this age group acquire half of the estimated 20 million new STDs diagnosed each year.”).

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Endnote 38

http://www.susps.org/overview/birthrates.html (“Each year there are approximately 4 million births in the U.S.”).


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