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Intrauterine Devices (IUDs)
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Section 1

- Introduction
- Objectives
- Safety
- Overview
- Early IUDs
- Copper IUDs
> Mechanisms
- Failure Rates
- Comparison
- Method Costs
- Characteristics
- Characteristics
- Incidence Rate
- Reducing Risk
- Perforations
- Ectopic
- Expulsions
- Rates

Section 2
Section 3


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Section 1 - Intrauterine Devices (IUDs)

Mechanisms of Action of Copper IUDs

Prevents fertilization by:

  • Impairing the viability
    of the sperm

  • Interfering with sperm movement
Copper IUD in uterus

Slide 7

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.



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