Birth Control Effectiveness and Failure Rates

Birth Control Effectiveness

If you're worried about getting pregnant, it's important to understand birth control effectiveness. Most methods will reduce the chance of a pregnancy, but some work better than others.

Understanding Birth Control Effectiveness

Selecting the right method is a matter not just of choosing an effective form of birth control, but of choosing one that fits into your lifestyle. All methods have two separate effectiveness ratings: one based on "perfect" use and one based on "typical" use. That second rating takes into account real-world errors, including things like putting the condom on too late or missing a dose of the birth control pill.

If you have trouble remembering pills or don't like to use condoms, effectiveness is likely to be much lower than if you choose a method that you and your partner find easy to use.

The Pill

Different birth control pills contain hormones with different structures, and doses also differ from pill to pill. However, most pills on the market have approximately the same effectiveness.

According to Planned Parenthood, birth control effectiveness is very good with proper use of birth control pills. With perfect use over one year, less than one in 100 women will get pregnant. With typical use, about eight in 100 women will get pregnant.

In addition to forgetting a pill, there are some things that can reduce this method's effectiveness. They include:

  • Illnesses that cause vomiting (If you can't keep the pill down, it's the same as skipping a dose.)
  • Some antibiotics
  • Certain anti-fungal medicines which are taken by mouth
  • Some anti-seizure drugs
  • Some HIV drugs

The Patch and the Ring

The patch and the ring use hormones very similar to those in the pill, and effectiveness is about the same. The same medications that reduce birth control effectiveness for the pill can also interfere with the ring and the patch.

The Shot

The birth control shot (brand name Depo-Provera) is another hormonal method. It contains just one of the medications in the birth control pill, a hormone called progestin. The shot is a very effective method. According to the manufacturer, only 3 of 1,000 women will become pregnant over a year, with either perfect or typical use. Planned Parenthood states that typical use allows about 3 pregnancies per 100 women.

Aminoglutethimide, a medicine used to treat certain kinds of tumors, can decrease the shot's effectiveness. The manufacturer does not report any other drugs interacting with the shot, but always check with your doctor to be sure about any medicine you're taking.


Condoms are popular because they're inexpensive and readily available, they protect against STDs, and they don't involve any medication. However, they're not as reliable as some of the other methods. With perfect use, only two of 100 women will become pregnant over a year of using condoms. However, in real-life use, it's likely that up to 15 of 100 women will become pregnant. If birth control effectiveness is vital, you may want to consider using another method along with condoms.

Lubricants containing oil weaken condoms and reduce their effectiveness. Water-based lubricants are a better choice and may help protect the condom from breaking. Waiting too long to put the condom on can increase the chance of pregnancy, because some sperm may leak out before the man ejaculates. The condom should be put on as soon as the man's penis becomes erect.


IUDs are very common in Europe. They require very little maintenance and can be left in place for several years. In most cases, the chance of getting pregnant with an IUD is less than one woman per 100 per year.


A diaphragm is a small rubber disk that is inserted into the vagina before intercourse. It covers the cervix (the opening into the uterus) so that sperm can't get in. Used correctly, with spermicidal gel, diaphragms allow six pregnancies per 100 women per year. With typical use, about 16 of 100 women will become pregnant. Similar devices, such as the cervical cap and Lea's shield, have similar rates with typical use.

Correct Use Is Key

When used correctly, most forms of birth control have extremely high effectiveness ratings. If you have any questions at all about the proper use, don't hesitate to ask your doctor or pharmacist.

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Birth Control Effectiveness and Failure Rates