The degree of emergency contraceptive effectiveness depends on what kind of contraceptive is taken and how quickly it was taken after unprotected sex. In general, pills that contain only progestin are more effective than combined emergency pills. Plan B One Step and Next Choice are examples of emergency contraceptives that contain only progestin. Pills that contain an antiprogestin are more effective than progestin-only pills. Ella would be an example of this type of pill.
"Combined pills" contain both progestin and estrogen and they reduce the risk of pregnancy by 75%. Progestin-only emergency contraceptive pills that are taken within the first 24 hours after sex reduce the risk of pregnancy by up to 95%. Emergency contraceptives are safe and effective but not as effective as birth control used before or during sex, such as the birth control pill or condoms.