How Effective Is Emergency Contraception?

morning after pill statistics
How Reliable Is Emergency Contraception For Preventing Pregnancy?

If taken correctly, it is estimated that the emergency contraceptive pill (also called the morning after pill) is 90 to 95 percent effective in preventing pregnancy. Course, it's impossible to measure exactly how effective they are because no one knows for sure if conception would have occurred had the pills not been taken. There are a few different types of emergency contraceptives, and some are slightly more effective than others:

Progestin-Only Pills
Progestin-only morning after pills can be taken up to 72 hours after unprotected sexual intercourse (although recent research now indicates that they can even be taken up to 120 hours later). They reduce the risk of pregnancy by 88 percent. However, the sooner they are taken, the more effective they are. If taken within 24 hours, they reduce the risk by 95 percent. Progestin-only pills include Next Choice, Plan B One Step and Levonorgestrel Tablets and are available without a prescription from most pharmacies.

Ella (marketed as ellaOne in Europe) contains an ingredient called ulipristal acetate. Its main advantage is that it can effectively be taken up to 120 hours (5 days) after unprotected sex. The disadvantage is that it requires a prescription. Statistically Ella is slightly more effective in preventing pregnancy than progestin-only pills. Furthermore, it retains its potency - it is just as effective in preventing pregnancy on day one as on day 5 after sex.

Regular Birth Control Pills
Some brands of daily birth control pills, if taken in higher dosages, can be used as emergency contraceptives. Only certain brands are approved by the FDA for use in this way. You can see a complete list here: Can I use ordinary birth control pills for emergency contraception? Taking daily birth control pills in the recommended dosage as an emergency contraception can cut your chance of pregnancy by about 75 percent. You may also find this question useful: What is the difference between the emergency contraception pill and the normal pill?

How Does It Work?
The emergency contraceptive pills which are sold in the United States and Europe will never cause an abortion. In other words they cannot end a pregnancy once it has begun. This is why they are not effective if taken after 120 hours - because a pregnancy will have begun by then if it was going to. If taken within the correct time frame, emergency contraceptives work by preventing a pregnancy from starting. They do this by interfering with the ovulation process and slowing down the movement of the egg through the fallopian tube (so it's less likely to encounter sperm) or by altering the lining of the womb so implantation can't take place. In other words, emergency contraceptives are not abortion pills. The abortion pill (Mifeprex, also called RU-486 and mifepristone) is very different because it ends a confirmed pregnancy. It does this by making the womb expel the egg, ending the pregnancy, up to 49 days after it is confirmed. Mifeprex is only available after consultation with a doctor.

Related Questions
What is emergency contraception?
What are the first signs of pregnancy before a missed period?
Will I gain weight on the contraceptive pill?
Can you get pregnant while taking the pill?
Is it possible to be a little bit pregnant?

• Like more information? See Birth Control Methods
• Got another question? See: Womens Health Questions

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