After intercourse, ECPs may prevent pregnancy by preventing ovulation, blocking fertilization or preventing implantation of a fertilized egg. Combined ECPs ordinary oral contraceptive pills containing estrogen and progestin hormones Progestin-only ECPs or minipills regular oral contraceptive pills, taken in higher doses and containing progestin only. These have been used as ECPs for 30 years. According to both medical science and legal convention, pregnancy begins only after implantation of a fertilized egg in the uterus. ECPs therefore act to prevent a pregnancy.
Studies show that ECPs have no effect on established pregnancies.
Some extremist anti-choice groups oppose emergency contraception by equating it with abortion, which they also oppose. These groups are out of step with the mainstream medical community and their views find almost no support in laws and policies at the state and federal level. The attacks against ECPs are unwarranted and must therefore be seen as part of an agenda to ban all contraceptives. Emergency Contraceptive Pills Are Not RU-486. ECPs prevent pregnancy after sex.