What is the “morning after pill"?

The “morning-after pill" is a single treatment used as emergency contraception after unprotected sexual intercourse or contraceptive failure, for example a burst condom or missed pill. It is most effective if taken within 24 hours of sexual intercourse but must be taken within 72 hours to be effective in reducing the chances of becoming pregnant. This pill will not have any effect on an existing pregnancy.

How does emergency contraception work?

Levonorgestrel is the same synthetic progestogen that is used in combination contraceptive pills, but is used at a much higher dose for emergency contraception. When taken as a single one-off pill, high-dose levonorgestrel can prevent ovulation or implantation of a fertilised egg, depending at what stage of the menstrual cycle it is taken. If taken within the first two weeks of the cycle it will prevent ovulation before it has taken place, which is when likelihood of fertilisation is the highest. If taken in the second two weeks of the month it helps reduces the chances of implantation by preventing changes in the endometrium that are needed for implantation of the fertilised egg. The “morning-after pill" will not prevent a pregnancy continuing if fertilization and implantation have already taken place.
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