title: Post-ovulatory contraception.
abstract: It is possible to prevent pregnancy after unprotected intercourse by suppressing ovulation, inhibiting fertilization or interfering with tubal transport and/or implantation of the early embryo. IUCDs probably prevent implantation by stimulating the release of prostaglandins from the endometrium but are not acceptable to many women. Post-coital contraceptive steroids, e.g. high-dose oestrogens, are associated with a relatively high incidence of side-effects and must be taken within 72 hours of coitus. As these agents are effective by creating a uterine environment unfavourable for implantation, it may be possible to use antigestagens or antioestrogens in this way. It is already known that an antigestagen in combination with a prostaglandin is a highly effective method of inducing abortion in very early pregnancy. The corpus luteum is essential for the maintenance of pregnancy and its destruction by a luteolytic agent should dislodge the implanting embryo. If an effective method of preventing implantation could be developed which was relatively free from side-effects, it should be possible to use it as a regular form of contraception to be taken only when the risk of pregnancy had occurred.
authors.forename: A
authors.initials: A
authors.lastname: Glasier
authors.forename: D T
authors.initials: DT
authors.lastname: Baird
mesh_terms: D003281:Contraceptives, Postcoital / Q000009:adverse effects / Q000494:pharmacology*; D005260:Female; D006801:Humans; D011247:Pregnancy; D012098:Reproduction / Q000187:drug effects
chemical_list: D003281:Contraceptives, Postcoital