Mechanism of Action of Intrauterine Contraceptives in Women

Because the primary mechanism of action of intrauterine devices in women is not clearly understood, the development of improved IUDʼs has been impeded. A great variety of empirically designed devices, largely of linear polyethylene plastic, have been inserted into millions of women during the past decade, often with results inferior to those obtained by Grüfenberg 40 years ago. Therefore, an analysis of factors which could be responsible for variations in IUD efficacy was undertaken. The evidence in hand indicates that a chemotactically mediated, local endometrial response to the device prevents conception. A shield intrauterine device, engineered to take advantage of this principle, has demonstrated a 98.9% efficacy, providing direct experimental support for the surface interaction hypothesis.