[Mode of action of intrauterine devices]

The intrauterine foreign bodies (IUFB) used in a series of the authors' experiments were made of stainless steel, plastics, copper wire, and silicone rubber. The experiments were done as follows: Firstly, the implantive influence of IUFB was examined. It was found (1) that the embryo might be implanted above or below the position of the foreign body but not at the position of the foreign body and (2) that the existing 5 different kinds of foreign bodies possessed the same antifertility effect. Secondly, the washing fluid of uterine cavities with foreign bodies was examined for studying biochemical component, immunologic reaction in respect of blood coagulating factors and white cell counts and its differential counts. The results of these experiments did not give any significant statistical meaning except in so far as the protein nitrogen and white cell counts were concerned. The authors have investigated the results of the contrast group by statistical methods, which showed no significant change, but it was found that the polymorphonuclear leukocyte counts are proportional to the amount of protein nitrogen contained. In the experiments, the authors did not observe any relationship existing between the uterine foreign bodies and the increase of macrophages. Thirdly, the morphology of the endometrium in contact with intrauterine foreign bodies was examined by light, scanning, and transmission electron microscopy. The results of these observations showed that the phenomenon of the endometrium can be divided into 3 conditions: (1) the accumulated mucus formed a thin or thick layer like a screen covering the surface of the endometrium; (2) the erosions and ulcers appeared on the surface of the endometrium with some white cell infiltration; and (3) sometimes, necrosis of the endometrium and bleeding ensued, 1 or another of these phenomena might happen in all the samples but one. The authors, therefore, conclude that the antifertility effect of an interauterine foreign body must prevent the embryo from implantation. This effect may be caused by the pressure and stimulation of the foreign bodies, which induce unspecialized reaction with moderate exudation and necrosis in the tissue.