Plan B Pill Effectiveness


Plan B is a type of emergency contraception that can be used after unprotected sex to help prevent pregnancy. 7 out of 8 women who would have gotten pregnant without using Plan B did not get pregnant after using it. Some examples of when a woman may need to use Plan B would be:

  • • When she has sexual intercourse without birth control or contraception.
  • • When the condom breaks or comes off.
  • • When she forgets to take her birth control pill
  • • When she uses her current method incorrectly or inconsistently.
  • • When she has been sexually assaulted.

The sooner you take Plan B after unprotected sex the better effectiveness it has against pregnancy. If taken within 72 hours after unprotected intercourse Plan B has an 89% chance of successfully preventing a pregnancy. However, if taken within 24 hours after unprotected intercourse the effectiveness rate goes up to 95%. So again, the sooner Plan B is taken, the better chance it has of working. Just because it is called the morning after pill does not mean a woman has to wait until the next morning to take it. It can be taken immediately after unprotected sex.

It is important to remember that for Plan B to be effective the woman must take BOTH doses. The first dose as soon as possible after unprotected intercourse, the second dose 12 hours later. If only one dose is taken, the risk for effectiveness increases. There is also Plan B one step which is a single dose of emergency contraception that should be taken as soon as possible after unprotected intercourse.

Plan B works by preventing ovulation if it has not already occurred at the time of unprotected sex. If ovulation has already occurred, Plan B will prevent an egg from implanting in the uterus, usually by causing the lining of the uterus to shed earlier than her next scheduled menstrual cycle. If there is already an established pregnancy, Plan B will not disrupt it. Plan B and other forms of emergency contraception should not be used confused with RU486, which is a pill that terminates a pregnancy in its earliest stages.

Plan B is designed as a back up emergency method of contraception and should be used accordingly. It is not recommended to use Plan B or any other form of emergency contraception as a regular method of birth control.

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