Plan B is highly effective when taken within 12 hours after unprotected sex, with an effectiveness rate of about 95% or higher. The sooner it is taken, the better it works to prevent pregnancy by delaying ovulation. Its effectiveness decreases as time passes after unprotected sex, and it is best taken as soon as possible within the approved 72-hour window.
Effectiveness Details
- Within 12 to 24 hours: Plan B is approximately 95% effective at preventing pregnancy.
- Within 72 hours: Effectiveness decreases to about 60-94%, with the best results closer to the time of sex.
- Mechanism: Works by temporarily delaying ovulation to prevent fertilization.
- Not effective if ovulation has already occurred or if pregnancy is established.
Additional Notes
- Plan B is not an abortion pill; it does not terminate an existing pregnancy.
- It can be taken with or without food.
- More effective for women with normal body weight; less effective for women with BMI over 30.
- For higher BMI individuals or later intervention, copper IUD is a more effective emergency contraception.
Therefore, taking Plan B within 12 hours after unprotected sex gives the highest chance of preventing pregnancy.
