How are intrauterine devices (IUDs) used for contraception?

Updated: Dec 10, 2018
  • Author: Frances E Casey, MD, MPH; Chief Editor: Richard Scott Lucidi, MD, FACOG  more...
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The intrauterine device is one of the most effective contraceptive devices available with pregnancy rates < 1%.

The first FDA approved intrauterine device in the United States was the Dalkon shield, withdrawn in the 1970s due to a series of litigations related to septicemia.  The copper and progesterone intrauterine devices available now are not associated with severe infections, but practitioners should screen for chlamydia and gonorrhea according to CDC guidelines at time of placement to prevent development of pelvic inflammatory disease.

The intrauterine device is gaining in popularity in the United States with nearly a 5-fold increase in use among US women aged 15 to 44 years from 1.5% in 2002 to 6.8% in 2011-2015. [18, 19]

The Copper T380 was introduced in 1988. The T-shaped IUD is made of polyethylene with fine copper wire wrapped around the vertical stem. The string is clear or white and hangs from the lower limb of the IUD. This device consists of 308 mg of copper covering portions of its stem and arms.  A foreign-body reaction creates a toxic intrauterine milieu, preventing fertilization as its primary mechanism of action. Contraceptive effectiveness continues for 12 years.

The levonorgestrel intrauterine system (LNG-IUS) causes cervical mucus to be thicker in consistency, thereby altering sperm migration. Uterotubal fluid and motility changes inhibit sperm migration. IUDs also result in endometrial suppression. [20]

In December 2000, the FDA approved another form of IUD, the levonorgestrel intrauterine system termed Mirena (Berlex Laboratories; Montville, NJ). More than 2 million women in Europe have used this form of contraception in the past decade with great success. [21]   Mirena is similar in shape to the Copper T380 in that it also consists of a small T-shaped frame with a reservoir that contains levonorgestrel, a progesterone. This intrauterine system releases 20 mcg of levonorgestrel per day into the uterine cavity for as long as 7 years. It consists of a polyethylene frame with a cylinder containing a polydimethylsiloxane-levonorgestrel mixture enveloping the vertical arm. The cylinder is coated with a membrane that regulates the release of the hormone. This model is also visible on x-ray films. The Mirena device now has FDA labelling for treating menorrhagia as well. [22, 23]   In 2015, the FDA approved Liletta, also a 52mg levonorgestrel intrauterine device, with a release rate of 19.5mcg/day that declines to 9.8mcg/day at 5 years of use.  Extended use studies are ongoing. [24]

In January 2013, the FDA approved Skyla, another T-shaped polyethylene device designed to prevent pregnancy for 3 years, during which time it releases a diminishing dosage of levonorgestrel. The Skyla IUD contains 13.5 mg of levonorgestrel that releases at a rate of 14 mcg/day (after 24 days from insertion). The release rate declines after 3 years to 5 mcg/day.  With lower rates of levonorgestrel release, Skyla is associated with increased spotting and the cumulative 3-year pregnancy rate, based on 10 pregnancies, estimated by the Kaplan-Meier method was 0.9 per 100 women or 0.9%, with a 95% upper confidence limit of 1.7%.  [25]  Kyleena, a 19.5mg levonorgestrel device, FDA approved to 5 years of use, has a similar 3-year pregnancy rate. [26]

Insertion of an intrauterine device in the immediate postpartum period provides an opportunity for placement that some patients may not have otherwise.  Immediate postplacental placement is associated with an increased risk of expulsion (10-20%) but these expulsions are typically immediately recognized and studies have demonstrated high continuation rates at 6 months and 1 year. [27, 28] Immediate postcesarean insertion has expulsion rates similar to interval placement. Rates of infection are not increased as compared to interval insertion.

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