[Mechanism of action of intrauterine devices].

Abstract

The article describes the various types of IUDs either inert or active presently in use in Mexican Family planning programs. Possible mechanisms of action are discussed among which a migration of leukocytes to the endometrium and miometrium and consequent liberation of embriotoxic substances which destroy the blastocyte. Enzymatic and biochemical changes in the endometrium are also possible as is a decrease in immunologic tolerance to implantation. Copper IUDs may act by direct toxicity and progesterone-releasing IUDs by maintaining a continuous progestational effect in the endometrium thus inhibiting nidation and spermatic capacity. (Summary in ENG)