Plan B One-Step (morning after pill) is intended to prevent pregnancy after known or suspected contraceptive failure, unprotected intercourse or forced sex. It contains large amounts of levonorgestrel, a progestin hormone found in some birth control pills. It may work by preventing the egg and sperm from meeting by delaying ovulation; it won’t disrupt an implanted pregnancy, but may prevent a newly formed life from implanting in the uterus (2).
Plan B One-Step consists of one pill taken within 72 hours of sex (2).
Side effects may include changes in periods, nausea, lower abdominal pain, fatigue, headaches and dizziness. If your period is more than a week late, you may be pregnant from a prior sexual encounter. Plan B One-Step should not be taken during pregnancy nor used as a routine form of birth control.(2)
There is evidence that Plan B One-Step use may increase the risk of ectopic (tubal) pregnancy, a potentially life threatening condition.(2) Women who have severe abdominal pain may have an ectopic (tubal) pregnancy, and should get immediate medical help.
There are no long-term studies on the safety of Plan B One-Step in women under 17, after repeated use or the effects on future fertility.(2)