Postinor or morning after pill as it's popularly called in the UK is a medication that women uses to prevent pregnancy after unprotected sex, it serves as emergency contraceptive. It has 95% chances of preventing pregnancy if used within 24 hours after sex and 85% if used after 24 hours.
The UK government believes so much in its effectiveness that they made it free for teenage girls. Well below are the few side effects of it.