Do You Know Your IUDs?

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The topic of birth control methods can be confusing. Even if you had sexual education classes in elementary or high school, the information may now be a vague memory. You are not alone, as most North Americans tend to have only a limited knowledge of the pill and condoms. One of the least discusses birth control methods is the intrauterine device (IUD) and the intrauterine system (IUS).

The first IUD (a device that fits entirely in the uterus) was marketed in 1929 by a German gynecologist named Ernst Gräfenberg. The ring-shaped IUD was made of silk threads, and only 3% of the 1,100 women who used it became pregnant. In 1930, he improved the device by covering the silk thread with a fine silver wire. Dr. Gräfenberg was unaware that the silver contained 26% copper, which reduced the pregnancy rate to 1.6% in 600 of the users. The copper provoked an inflammatory response in the uterus that created a hostile environment for sperm.

Over the years, various doctors improved the original IUD (see diagram below). For instance, the IUD became T-shaped, similar to the shape of the uterus, and this reconfiguration lowered its expulsion rate from the uterus. The device became smaller with one filament tail at its end, which made it more comfortable for women. By the 1970s, IUDs were made of plastic, with greater surface areas of copper, and consistently had pregnancy rates of less than 1%.

IUDs are the world’s most widely used long-term reversible birth control method, with nearly 160 million users (about 2/3 of them being Chinese). In North America, only 2.9% of Canadian women and 1.8% of American women use IUDs. One of the reasons for its lack of popularity in the Western world is its perceived health risks.

In 1971, A.H. Robins Company manufactured and sold the Dalton Shield plastic IUD in North America. By 1974, this IUD was removed from the market by the US Food and Drug Administration (FDA) because there were reports of miscarriages, infections, infertility, and death resulting from using this device. The IUDs that are now available on the market do not put women’s health at risk. Fears of increased ectopic pregnancy or pelvic inflammatory disease are unfounded.

In North America, the two most popular types of IUDs are the copper ParaGard by Duramed Pharmaceuticals and the hormonal Mirena by Bayer.

ParaGard T 380a is a T-shaped plastic frame wrapped with pure electrolytic copper wire and/or copper collars (see diagram above). The number “380” refers to the surface area in square millimeters of copper contained in the IUD. The top of the T is 32 mm wide and the vertical part is 36 mm long. The arms hold the device in place near the top of the uterus.

The exact manner in which the IUD prevents pregnancy is still unclear, but there are a few theories. For instance, the presence of ParaGard in the uterus provokes the release of leukocytes (white blood cells) and prostaglandins (involved in the inflammation response) by the uterus lining (endometrium). These substances are toxic to both sperm and egg while copper increases T 380a’s toxicity to sperm. Some doctors have suggested that ParaGard prevents the implanted embryos from developing in the uterus. It is, for this reason, an IUD can be used as emergency contraception if inserted up to 5 days after unprotected intercourse.

The T 380a can be left in the uterus for 10 years and costs about $250. In the long run, it is one of the cheapest birth control methods. The IUD needs to be inserted by a licensed physician. Many women complain of pain during the procedure and non-steroid anti-inflammatory drugs (NSAIDS) are recommended. Most women experience heavier and more painful periods after the insertion of an IUD. There are very rare complications such as the expulsion of the device by the uterus during the first year, and uterine perforation during insertion.

In the early 1970s, the first hormonal IUSs containing natural progesterone became available to women. New IUSs using synthetic progesterone were marketed in 1976. By the 1990s, IUSs were extensively used in Europe. In North America, it was not until the year 2000, the FDA approved the levonorgestrel-releasing intrauterine system (LNG-IUS) marketed under the brand name Mirena.

Mirena consists of an inert T-shaped polyethylene frame to which on the vertical part, is attached a polydimethylsiloxane reservoir (see diagrams below). The reservoir contains 52 mg of levonorgestrel. This synthetic progesterone is released gradually through a silastic capsule, at a rate of 20 µg/day. The daily amount of progesterone released by the capsule is much lower than the birth control pill (20 µg/day versus 0.1 mg/day).

The LNG-IUS prevents pregnancy in a number of ways. In about 50% of women, the device stops ovulation. There is also a thickening of the cervical mucus in some users, which prevents the sperm from entering the uterus. Up to 66% of women have significant inflammation of the uterine wall, which may interfere with sperm function. Also, the endometrium produces Glycodelin A (a glycoprotein) in mid-cycle, which inhibits fertilization.

A licensed physician needs to insert the Minera (ideally) during the first 7 days of the patient’s menstrual cycle. The IUS has an annual pregnancy rate of 0.1-0.2%, lower than the copper IUD and similar to sterilization. Other benefits are reduced menstrual flow, which is associated with an increase in hemoglobin and blood iron levels. The LNG-IUS costs about $250 and can stay in the uterus for up to 5 years, making it cost-effective.

IUDs have come a long way since the Gräfenberg ring. Pharmaceutical companies are testing new prototypes that will help reduce the negative side effects of the current devices. Women now have, more than ever, better control over their own fertility.

Literary Truths

You should not be using the IUD ParaGard T 380a if you have:

• A current pelvic infection

• A sensitivity to copper or nickel

• Concerns that you may be pregnant

• Have given birth within the past 4 weeks

• Benign or malignant gestational trophoblastic disease

• High likelihood of exposure to Gonorrhea and Chlamydia

• AIDS (unless under control with antiretroviral therapy)

• Endometrial, ovarian or cervical cancer

• Distortion of the uterus (i.e., fibroids)

• Unexplained vaginal bleeding

• A very recent septic abortion

You should not be using the LNG-IUS (Mirena) if you have:

• A current pelvic infection

• Concerns that you may be pregnant

• A weak immune system

• Liver disease

• Unexplained vaginal bleeding

• Uterine, cervical or breast cancer

• A history of breast cancer, ectopic pregnancy, tubal disease (i.e., pelvic inflammatory disease)

• A distortion of the uterus (i.e., fibroids)

• An allergy/sensitivity to levonorgestrel, silicone or polyethylene

Truth in Motion

References

Canadian Women Under-using IUDs

Cao X., W. Zhang, G. Gao, H. Van Kets & D. Wildemeersch . “Randomized comparative trial in parous women of the frameless GyneFix® and the TCu380A intrauterine devices: long-term experience in a Chinese family planning clinic.” The European Journal of Contraception & Reproductive Health Care, Vol.5, Issue 2 April 2000:135-140

Contrel

Gastric acid

Grigorieva V., M. Chen-Mok , M. Tarasova, et al. “Use of a levonorgestrel-releasing intrauterine system to treat bleeding related to uterine leiomyomas.” Fertil Steril, (2003);79:1194-1198.

Gynefix

The GyneFix Intrauterine Device

IUS diagram

“Long-acting progestogen contraceptives.” The Practitioner (2002): 332.

Paladine, Heather L., C. E. Blenning, and D. Zegar Judkins. “What are contraindications to IUDs?” Journal of Family Practice 55.8 (2006): 726.

Planned Parenthood of Toronto: IUD

Silastic Capsule diagram

Zinger, Michael, and M. A. Thomas. “Using the levonorgestrel IUS.” Contemporary OB/GYN 46.5 (2001): 35.