Intrauterine Devices: Contraceptive method
Intrauterine devices are plastic, polyethylene devices impregnated with barium sulfate to make them radiographic, now containing copper or progesterone, which stay in the uterine cavity. They cause a sterile spermicidal inflammatory reaction. Very few sperm reach the oviducts, and fertilization usually does not occur. If it should occur, implantation is prohibited due to effect on the endometrium. There are two IUDs currently marketed in the United States. “ParaGard” (TCu-380A) is a copper-containing IUD with an efficacy lasting ten years. “Mirena” is a progestin-releasing IUD which must be replaced every 5 years.
First-year IUD failure rates range from < 1 % to 3.7 %. Pregnancy usually follows spontaneous expulsion of the IUD, occurring most commonly shortly after insertion. Cumulative four to six year pregnancy rates are less than 1 % per year. An experienced clinician has fewer failures, due mainly to correct high-fundal insertion.
The advantage of the IUD include its use in women unable to take estrogen, lack of systemic side effects, immediate high efficacy, a rapid return to fertility after removal, the necessity for a single motivational act, and a lack of interference with lactation. The disadvantages are a slight increased risk of infection during the month following insertion, an increase in menstrual bleeding and cramping with the copper IUD (the progestin IUD decreases blood loss and dysmenorrhea), and the rare complications of expulsion and perforation.
Pregnancies may occur with the IUD in place. This carries about a 55% risk of spontaneous abortion. Removal of the IUD after pregnancy is diagnosed lowers this risk to about 25%. There may be a higher risk of septic (spontaneous) abortion, but with modern IUDs this is not certain. IUDs substantially decrease the risk of ectopic pregnancies compared to not using contraception, but they are more effective at preventing intrauterine than preventing ectopic pregnancies. If a woman using an IUD does become pregnant, she has a higher chance of having an ectopic pregnancy (3-4% with the copper IUD 1.5% in the general population).
Concerns regarding the safety of the IUD relate mostly to pelvic inflammatory disease (PID) and subsequent infertility. Although these concerns are unwarranted with modern IUDs, the American public is still suspicious of this very effective contraceptive. The Dalkon Shield was found to be the main offender and was removed from the market. Other IUDs were removed from the market because of the cost of defending against multiple malpractice suits.
The incidence of PID in IUD users is greater than background risk only in the first 20 days after insertion and is thought to be related to bacterial contamination of the endometrium at the time of insertion. Long term IUD use does not increase infection risk, and there is emerging data that suggests a possible protective effect against pelvic infection. Sexual behavior is the most important modifier of infection risk; ideal IUD candidates should be at low risk of sexually transmitted infection, and all women should be counseled to use condoms whenever they have intercourse with a potential carrier.
Contraindications for IUD use include:
- Known or suspected pregnancy
- Acute PID, or current behavior suggesting a high risk for PID (woman or partner has multiple sexual partners)
- Postpartum or post-abortal endometritis in the past 3 months
- Distorted uterine cavity from leiomyomata, uterine anomalies, etc.
- Undiagnosed abnormal genital bleeding
- Known or suspected cervical or uterine malignancy, including an unresolved abnormal Pap
- Untreated acute cervicitis or vaginitis
- Conditions associated with increased susceptibility to infection (AIDS, leukemia, IV drug use)
- Previous ectopic pregnancy or condition that would predispose to ectopic pregnancy
- A previously placed IUD that has not been removed
In addition, the copper IUD should not be used in women with a copper allergy or Wilson’s disease. The progestin containing IUD (Mirena) should not be used in a woman with a previous adverse reaction to levonorgestrel, in a woman with significant active liver disease [mild elevation in LFTs from chronic hepatitis B or C is not a contraindication], or breast cancer.