Intrauterine Contraceptives

Key Points

• IUCs are among the most effective forms of contraception available.

• Although preventing fertilization, IUCs are not abortifacients.

• Adolescents can safely use IUCs but underuse this method.

• The levonorgestrel IUC is an effective treatment for menorrhagia and can decrease the risk of ascending genital tract infections.

• IUCs do not increase the risk of PID outside the first 20 days after insertion.

• The copper-T380A IUD can be used as emergency contraception.

Intrauterine contraceptives (IUCs) are small, T-shaped devices inserted into the uterine cavity by a medical provider. IUCs provide excellent long-term, reversible contraception. The two IUCs currently available in the United States are the copper-T380A intrauterine device (IUD) (TCu380A, Para-gard) and the levonorgestrel intrauterine system (LNG-IUS, Mirena). In 2007 the American College of Obstetricians and Gynecologists (ACOG) concluded that modern IUCs are an excellent contraceptive choice for adolescents and are underused by this population. Contrary to popular belief, both IUCs act by inhibiting fertilization and are not abortifacients (Grimes, 2007; WHO, 1987) (Level A).

Copper-T380A Intrauterine Device

The TCu380A (Paragard in U.S.) is a polyethylene IUD with copper wire wound on the stem and copper sleeves on each of the arms, for a total of 380 mm2 of exposed copper surface area. Although FDA approved for 10 years' use, it has proved efficacious for at least 12 years (UN/WHO, 1997) (Level A).

Mechanism of Action

Copper ions released from this IUD act as a spermicide to inhibit sperm motility and the acrosomal enzyme reaction. In addition, increased macrophages in tubal and uterine fluids act to phagocytize sperm.

Advantages

Among the most effective forms of contraception available, IUCs are long acting but easily reversible, with rapid return to fertility. Nonhormonal methods may be preferable to some women. IUCs may be used by those with a contraindication to estrogen use. IUDs decrease the risk of endometrial and possibly cervical cancer (Hubacher and Grimes, 2002). IUCs can be used as emergency contraception.

Disadvantages

The IUC must be placed and removed by a health care provider. IUCs may cause increased menstrual bleeding and dysmenorrhea. The IUD does not offer protection against STIs. There is increased risk of upper tract infection the first 20 days after insertion, but otherwise no increased risk of PID (Grimes and Schulz, 1999) (Level A).

Levonorgestrel Intrauterine System

The LNG-IUS (Mirena in U.S.) contains a steroid reservoir around the stem that releases 20 ^.g of levonorgestrel per day into the uterine cavity. Although FDA approved for 5 years' use, it has proven efficacy for at least 7 years (Sivin et al., 1991) (Level A).

Mechanism of Action

The main mechanism of action of the LNG-IUS is thickening of the cervical mucus, which blocks sperm access to the upper genital tract. In addition, changes in tubal fluid can impair both sperm and egg motility. There is occasional inhibition of ovulation (~20% of cycles).

Advantages

Among the most effective forms of contraception available, the LNG-IUS is long acting but easily reversible, with rapid return to fertility. Benefits include decreased menstrual flow and dysmenorrhea and effective treatment for menorrhagia. Thickened cervical mucus may contribute to decreased risk of ascending cervical infections (decreased rates of PID), especially in patients under 25 years old (Toivonen et al., 1991). The IUS may be used by women with contraindication to estrogen use. It decreases the risk of endometrial and possibly cervical cancer (Hubacher and Grimes, 2002).

Disadvantages

The LVG-IUS must be placed and removed by a health care provider. Amenorrhea may concern some women. It offers no protection against cervicitis or viral STIs. Risk of upper tract infection is increased in the first 20 days after insertion, but otherwise there is no increased risk of PID (Grimes and Schulz, 1999) (Level A). Some women may experience mild hormonal side effects, including headaches, breast discomfort, and acne.

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