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  • Title: Mechanism of action of intra-uterine devices (IUCD).
    Author: George MS.
    Journal: Antiseptic; 1968 Nov; 65(11):847-53. PubMed ID: 12254322.
    Abstract:
    At the IUD conference held in New York City in 1962 several discussions took place on the mechanism of contraceptive action of these devices. Whether it is something that happens to the fertilized ovum or something that happens after nidation was considered important. If it can be shown that IUDs operate as abortifacients, it was considered to become a philosophical and religious as well as a physiological problem. A number of possibilities were discussed. Ovulation had been shown to occur. Changes in the peristaltic pattern of the tubes had been shown to take place. It was thought that the fertilized egg may pass through the tube more quickly than normal and arrive in the uterus before it is capable of implantation. Patients who become pregnant with the device in place are considered to lack the reflex from the tube so that the egg goes through in the normal time and is mature enough for implantation when it arrives in the uterus. It was also considered possible that there is an interference with the ascent of the sperm to the area of fertilization. This might be at the level of the cervix, in the uterus, or in the fallopian tubes. It became apparent at the conference that little was known concerning the mode of action of IUDs in humans or in animals. The International Planned Parenthood Federation's report in 1966 states that the action of the IUD is unproven. There was no evidence that IUDs produce preclinical abortions or that endometrial changes preclude implantation. Sperm migration had occurred in the normal fashion. Changes in uterine or tubal motility were not considered important. The low incidence of tubal as well as intrauterine implantation suggested a mechanism that involves more than the uterine environment. There was some evidence that sperm and ova may not usually unite at all. It has been suggested that the foreign body in the uterus produces a toxic substance that does not allow the fertilized ovum to develop. The conclusion was that in humans fitted with an IUD something happens to the egg between the time of ovulation and nidation because there is no evidence of implantation. Whether the egg becomes fertilized was not established.
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