Mechanism of action of intrauterine contraceptive devices and its relation to informed consent, ,

The purposes of this review are to evaluate the available evidence for the mechanisms of action of copper-impregnated intrauterine contraceptive devices and to describe the informed consent consequences of those mechanisms. The medical literature was reviewed with the use of the Bioethics and Medline databases (1966 to present). Reports that supported or refuted the two major postulated mechanisms (interference with implantation of the fertilized ovum or spermicidal inhibition of fertilization) were assessed for their relative strength and support for the exclusivity of one or the other mechanism. The analysis of the evidence strongly suggests that the contraceptive effectiveness of intrauterine contraceptive devices is achieved by both a prefertilization spermicidal action and a postfertilization inhibition of uterine implantation. Patient informed consent for intrauterine contraceptive device insertion should include a discussion of these mechanisms of actions so as to avoid their use in patients with moral objections to postfertilization contraception.(Am J Obstet Gynecol 1997;176:503-6.)