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)
|Implant||less than 1%|
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.