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emergency contraception

Alternative Names
postcoital contraception, emergency birth control, morning after pill

Emergency contraception, or birth control, is therapy offered to women to prevent pregnancy after they have had unprotected sex.

What is the information for this topic?
Of those women who take emergency contraceptive pills after a single episode of unprotected sex, 97% will avoid pregnancy.

Regular birth control is the best way to prevent the need for this therapy. Safer sex practices using condoms are advised. A back-up method in case a condom breaks is also advised. In the event of a failed birth control method or rape, this therapy can be given right away.

Emergency birth control involves the use of high-dose hormone pills or the placement of an intrauterine device (IUD). Two methods of emergency birth control are available in Australia:
  • regular combined birth control pills, or "the pill," containing ethinyl oestradiol and norgestrel or levonorgestrel.
  • a copper-containing IUD. A doctor must insert this device through the vagina and into the uterus. It also needs to be removed at a later date.
The birth control pills are taken in two doses. The first dose is given within 72 hours of unprotected sex, but research has shown that it is most effective if taken within 24 hours of unprotected sex. The second is taken exactly 12 hours later. This method prevents pregnancy in 75% of cases. The pills that contain only one hormone prevent pregnancy in 85% of cases.

Insertion of an IUD within 5 days of unprotected sex works 99% of the time. Lack of knowledge, high cost, and trouble finding a doctor to insert the IUD has limited its use.

The risks of pregnancy must be weighed against the risks of emergency birth control. Short-term use of birth control pills does not have the same problems as long-term use. Women who may not be able to use birth control pills regularly may be able to use them safely for emergency birth control. There are no known long-term risks linked to the use of emergency birth control pills.

Emergency birth control may increase the risk of ectopic pregnancy, should pregnancy occur after therapy. Ectopic pregnancies occur when the egg implants outside instead of inside the uterus. Among pregnancies that have occurred in women taking birth control pills with only one hormone, roughly 5% occur outside the uterus. There is also a higher risk of pregnancy outside the uterus, if pregnancy occurs, with use of an IUD.

There does not seem to be a harmful effect on a baby born after failed emergency birth control use. Even daily use of birth control pills during the first part of pregnancy has not been shown to cause problems.

Side effects of using emergency birth control pills include nausea, vomiting, headaches, and dizziness. Nausea occurs in about 50% of women and vomiting in 20% who take pills containing 2 hormones. The pills with only one hormone seem to have fewer side effects. About 25% of women will have nausea and 5% will throw up. Taking medication to prevent throwing up before each dose may help.

IUD use can cause abdominal cramping and carries a risk of putting a small hole in the uterus.

Normal female bleeding, or menstruation, occurs in almost all women within 21 days if pregnancy has been prevented. Women should have a pregnancy test if this does not occur.

Author: Eva Martin, MD
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

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