Emergency contraception prevents pregnancy if you did not use contraception or if your usual form of contraception failed. Emergency contraception should not be used as a form of long-term contraception. Talk to your doctor about the available options if you desire long-term contraception. The emergency contraceptive (EC) pills are the most common form of emergency contraception and are most effective when taken before ovulation. The more popular levonorgestrel EC pills like Plan B are expected to be taken within 72hrs. There’s another option (ulipristal acetate) that requires a prescription, and can be taken within 5 days. The EC pills are effective if taken before the release of an egg from the ovary (ovulation). The sooner you take the pill, the more effective it will be. Also, the effectiveness of the EC pills may be reduced if a woman has a high body mass index (BMI). Get medical advice if you vomit shortly after taking the EC pills. You might need to take another dose or ...