CBSE · Class 12 · Biology · Reproductive HealthExplain the working mechanism of copper-releasing Intrauterine Devices (IUDs) as contraceptives.

Intrauterine Devices (IUDs) are very popular and effective methods of contraception inserted by doctors or expert nurses in the uterus through the vagina. Copper-releasing IUDs (such as CuT, Cu7, Multiload 375) function through specific biological mechanisms that prevent fertilization and implantation. First, the copper ions (Cu2+) released from the IUD suppress the motility of sperm. Spermatozoa require active flagellar movement to swim up the female reproductive tract to reach the fallopian tube; the toxic effect of copper ions drastically reduces their swimming speed and vitality, rendering them incapable of fertilizing the ovum. Second, copper ions increase phagocytosis of sperms within the uterus. The white blood cells, particularly macrophages, are stimulated by the presence of the device and copper ions to engulf and destroy sperms inside the uterine cavity. Third, the release of copper ions alters the biochemical environment of the uterine cavity, making the endometrium unsuitable for implantation. Even if fertilization fortuitously occurs, the hostile uterine lining prevents the blastocyst from successfully implanting, thereby preventing pregnancy.