What is the physiology of a copper Intrauterine Device (IUD)?

From the Guidelines

A copper intrauterine device (IUD) prevents pregnancy primarily through its toxic effect on sperm, creating a hostile environment that decreases sperm motility, viability, and fertilizing capacity, and also interferes with implantation by altering the endometrial environment. The copper IUD releases copper ions into the uterine and tubal fluids, producing biochemical changes that are spermicidal 1. Additionally, copper IUDs cause the release of prostaglandins and leukocytes, which further impair sperm function and migration through the female reproductive tract. If fertilization does occur despite these mechanisms, the copper IUD also interferes with implantation by altering the endometrial environment. The copper IUD does not affect ovulation or hormone levels, making it a non-hormonal contraceptive option. Copper IUDs (such as ParaGard) are effective immediately upon insertion, can remain in place for up to 10-12 years, and provide over 99% effectiveness in preventing pregnancy, as supported by recent guidelines 1.

Key Mechanisms of Action

• The copper IUD creates a hostile environment for sperm, decreasing their motility, viability, and fertilizing capacity.
• The device causes an inflammatory reaction in the endometrium, producing biochemical changes that are spermicidal.
• It also interferes with implantation by altering the endometrial environment.
• The release of prostaglandins and leukocytes further impairs sperm function and migration.

Clinical Considerations

• Copper IUDs are a non-hormonal contraceptive option and do not affect ovulation or hormone levels.
• They are effective immediately upon insertion and can remain in place for up to 10-12 years.
• The devices provide over 99% effectiveness in preventing pregnancy, making them a highly reliable form of contraception.
• Common side effects include unscheduled spotting or light bleeding, as well as heavy or prolonged bleeding, especially during the first 3-6 months of use, which can be managed with counseling and treatment options such as NSAIDs 1.

Recommendations

• Copper IUDs are a highly effective and safe contraceptive option for most women, including those with certain medical conditions, such as antiphospholipid antibody-positive patients, for whom estrogen-containing contraceptives are contraindicated 1.
• They can be used as emergency contraception within 5 days of unprotected intercourse.
• IUDs are also suitable for nulliparous adolescents and do not cause tubal infertility in nulliparous women.
• HIV infection is not a contraindication to IUD use, although women with advanced HIV disease may need to use alternative contraceptive methods until their immunologic and clinical status improves with antiretroviral therapy 1.

From the Research

Physiology of a Copper IUD

The copper Intrauterine Device (IUD) is a form of contraception that works by releasing copper ions, which creates a local inflammatory response to prevent fertilization 2. The device's primary mechanism of action is to make the uterine environment inhospitable for sperm, thereby preventing pregnancy.

Side Effects

Some women may experience side effects from the copper IUD, including increased uterine bleeding and pain, which may lead to early removal 3. However, research has shown that these side effects tend to decrease over time, with most bleeding and pain side effects improving during menses 3.

Corrosion Inhibitors

Studies have investigated the use of corrosion inhibitors, such as 6-mercaptopurine and pterin, to reduce the harmful release of copper ions and minimize side effects 4. These treatments have been shown to reduce the burst release effect of copper in simulated uterine solutions and improve the biocompatibility of the device.

Effectiveness and Comparison to Other IUDs

The copper IUD has been compared to other IUDs in terms of effectiveness and side effects, with some studies suggesting that certain types of copper IUDs, such as the TCu380A, are more effective in preventing pregnancy than others 5. However, there is no evidence that any particular framed copper device is better suited to women who have not had children.

Cancer Risk Reduction

Research has also explored the potential benefits of copper IUD use in reducing the risk of gynecologic cancers, including endometrial, cervical, and ovarian cancer 2. The available evidence suggests that both levonorgestrel and copper IUDs may reduce the risk of these cancers, although the mechanisms of action and protective effects may vary depending on the type of IUD.

Local Tissue Effects

The local tissue effects of copper-containing IUDs have been studied, with some research highlighting the potential for local injury caused by copper ions 6. However, the contraceptive effects of the copper IUD are thought to be enhanced by these local tissue effects.

• Key points about the physiology of a copper IUD:
  • The copper IUD works by releasing copper ions, which creates a local inflammatory response to prevent fertilization
  • Side effects, such as increased uterine bleeding and pain, may occur but tend to decrease over time
  • Corrosion inhibitors, such as 6-mercaptopurine and pterin, may reduce the harmful release of copper ions and minimize side effects
  • The copper IUD has been shown to be effective in preventing pregnancy, with some types being more effective than others
  • Copper IUD use may reduce the risk of gynecologic cancers, including endometrial, cervical, and ovarian cancer
  • Local tissue effects of copper-containing IUDs may include local injury caused by copper ions, but these effects are thought to enhance the contraceptive effects of the device 3, 4, 5, 2, 6