|
Prevents fertilization by:
- Impairing the viability
of the sperm
- Interfering with sperm movement
|
 |
All the mechanisms of action of copper-bearing IUDs are still
not completely understood. However, researchers believe that
the main mechanism of action of copper-bearing IUDs is the prevention
of fertilization. The presence of the IUD in the uterine cavity
creates a local inflammatory reaction thatappears to prevent sperm from reaching the fallopian
tubes. In addition, copper-bearing IUDs release copper inside
the uterus and the fallopian tubes, enhancing the debilitating
effect on sperm. Studies have generally found that sperm are
not as viable among IUD users, compared to other women.
Originally, it was thought that IUDs produced changes in the
uterus that either destroyed a fertilized egg or prevented a
fertilized egg from implanting in the uterus. However, it appears
that the IUD effectively interrupts the reproductive process
before implantation by preventing fertilization. The evidence
suggests that fewer sperm reach the site of fertilization in
women using IUDs than in women who are not using the device,
and, for women using copper devices, the sperm may not be able
to fertilize the egg. In two studies of women using mainly copper
IUDs, there was evidence of fertilization in less than 1 percent
of their cycles. In those few cases where fertilization does
occur, the IUD may prevent pregnancy by interfering with implantation
in the uterine cavity. However, in most cases the evidence has
shown that copper IUDs act prior to fertilization.
|
