What are the types of intrauterine devices (IUDs)?

Types of Intrauterine Devices (IUDs)

Two Main Categories

There are two fundamental types of IUDs available: copper-bearing devices and levonorgestrel-releasing (hormonal) devices. 1, 2, 3

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Copper IUDs

Available Products

• Copper T380A (ParaGard) is the only copper IUD available in the United States 4
• Contains a copper surface area of 380 mm² distributed across 3 arms of a T-shaped frame 5

Duration and Efficacy

• Approved for 10 years of continuous use with a failure rate of less than 1% 4
• Can be inserted at any time during the menstrual cycle if pregnancy is reasonably excluded 4
• Serves as the most effective emergency contraception when inserted within 5 days of unprotected intercourse, preventing over 95% of unwanted pregnancies 4, 6

Key Characteristics

• Contains no hormones and works primarily by preventing fertilization through copper's toxic effect on sperm 1, 3
• Does not protect against sexually transmitted infections or HIV 4
• Main side effect is increased menstrual bleeding and cramping, which may persist with long-term use 2, 7

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Levonorgestrel-Releasing (Hormonal) IUDs

Available Products in the United States

Three levonorgestrel IUDs are currently FDA-approved: 2

1. Mirena (52 mg levonorgestrel reservoir)

   • Releases 20 mcg of levonorgestrel per 24 hours 2, 7
   • FDA-approved for 5 years, but effective for up to 7 years 2
   • Cumulative failure rate of only 0.68% during years 6-8 2

2. Liletta (52 mg levonorgestrel reservoir)

   • Also releases 20 mcg per 24 hours 2
   • Currently approved for 3 years (though this may be extended) 2

3. Skyla (13.5 mg levonorgestrel reservoir)

   • Releases 14 mcg of levonorgestrel per 24 hours 2, 7
   • Approved for 3 years of use 2
   • Lower-dose option introduced in 2013 2

Mechanism of Action

• Primary mechanism is preventing fertilization by inhibiting sperm motility and thickening cervical mucus, with all mechanisms occurring before implantation 2
• Classified as progestin-only contraceptives containing no estrogen 2, 3

Therapeutic Benefits Beyond Contraception

Levonorgestrel IUDs provide significant non-contraceptive benefits: 2

• 71-95% reduction in menstrual blood loss with the 20 mcg/day devices (Mirena and Liletta) 2
• Many women experience lighter periods or complete amenorrhea 2
• Only Mirena has been formally evaluated and proven effective for treating heavy menstrual bleeding; lower-dose devices like Skyla have not been studied for this indication 2
• Particularly useful for adolescents requiring long-term menstrual suppression when estrogen is contraindicated 2
• Reduces dysmenorrhea and provides therapeutic benefits for endometriosis and adenomyosis 3

Side Effects

• Possible hormonal effects include headaches, nausea, breast tenderness, acne, depression, decreased libido, and functional ovarian cysts 7
• Irregular bleeding patterns are common initially, with 35% of women experiencing amenorrhea after 2 years 5
• Bleeding pattern changes do not correlate with contraceptive failure—the device remains effective regardless of bleeding 2

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Universal IUD Characteristics

Efficacy

• Both types have failure rates of less than 1% per year, making them among the most effective contraceptive methods available 2, 3, 5
• More effective than oral contraceptives used incorrectly 5

Safety Profile

• Safe for nulliparous women and adolescents—nulliparity is not a contraindication 2, 4
• Rapid return to fertility after removal 2
• Can be inserted immediately postpartum or post-abortion 4, 3
• Risk of pelvic infection is confined to the first 20-21 days after insertion; beyond this period, IUDs do not increase rates of STIs or PID 2, 4

Important Limitations

• Neither type protects against sexually transmitted infections or HIV 1, 4, 3
• Consistent and correct condom use is recommended if STI/HIV risk exists 1, 4

Expulsion Risk

• Occurs in 5-10% of cases within 5 years, with higher rates in younger nulliparous women 4, 5
• Women with uterine fibroids have approximately 11% expulsion risk versus 0-3% in women without fibroids 2

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Clinical Selection Algorithm

For contraception only:

• Either copper or levonorgestrel IUD is appropriate based on patient preference and contraindications 3
• Choose copper IUD for women with contraindications to hormones (history of thromboembolism, cardiovascular disease, breast cancer) 5

For heavy menstrual bleeding:

• Select Mirena or Liletta specifically—these 20 mcg/day devices have established evidence for treating menorrhagia 2
• Skyla has not been studied for this therapeutic indication 2

For emergency contraception:

• Copper IUD is the only option—must be inserted within 5 days of unprotected intercourse 4, 6