Levonelle One Step contains a synthetic hormone like substance called levonorgestrel. It prevents pregnancy in 99% of situations when you take it within 72 hours of having unprotected sex.
It will not prevent a pregnancy every time and is more effective if you take it as soon as possible after unprotected sex. It is better to take it within 12 hours rather than delay until the third day.
Levonelle One Step is thought to work by:
- Stopping your ovaries from releasing an egg
- Preventing sperm from fertilising any egg you may have already released
Levonelle One Step can only prevent you becoming pregnant if you take it within 72 hours of unprotected sex. It does not work if you are already pregnant. If you have unprotected sex after taking Levonelle One Step, it will not stop you from becoming pregnant.
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