Progestin Intrauterine Device (IUD) (Mirena)

Effectiveness: More than 99 percent effective (less than 1 pregnancy per 100 women each year).

What is it? The IUD is a small T-shaped plastic device, about 1 to 1½ inches, with a string attached. A health care provider inserts the device through the cervix into the uterus, and it releases synthetic progestin.

How does it work? The IUD slows or stops movement of the sperm and egg by changing cervical mucus, fallopian tubes and the uterine lining. It also releases synthetic progestin hormone to prevent the ovaries from releasing an egg, similar to other forms of progestin-only birth control. It takes about 7 days for the hormonal IUD to start working, and it remains effective for 5 to 7 years.

STD protection: No; you will still need to use condoms if you are concerned about STDs.

Benefits: It allows women to feel more spontaneous about having sex. You don't have to remember to use daily birth control or to interrupt foreplay to use birth control. It may reduce menstrual cramps and make your periods lighter or make them stop completely. It can be used during breastfeeding. It lasts 5 to 7 years, and removal by your health care provider is quick and easy. You may be able to get pregnant quickly after its removal.

Disadvantages: You may experience spotting between periods, irregular periods and increased cramps for up to 6 months. Your periods may eventually stop. When your IUD is inserted, you may experience mild to moderate pain, cramping or backache for a few days. If you or your partner has other partners, your risk of uterine infection increases. As with other forms of hormonal birth control, there is a slightly increased risk of heart attack, stroke and blood clots. Serious complications are rare, but always talk with your health care provider about risks and benefits.

Availability: Requires visits to your health care provider for insertion and removal.

Cost: $500 to $1,000; protection lasts 5 to 7 years.*

Notes: You should check monthly to feel for the IUD's string at your cervix. In rare instances, the IUD may slip out of place. You should not use a Mirena IUD if: you have severe liver disease; you have or have had pelvic inflammatory disease (PID) or other conditions that may make you susceptible to pelvic infections; you have untreated acute cervicitis or vaginitis; you are or may be pregnant; you have breast cancer or uterine or cervical tumors; you have uterine abnormalities including fibroids that distort the uterine cavity; you have unexplained vaginal bleeding; or you have an unresolved abnormal Pap test. Your health care provider also may determine that your uterus doesn't allow correct placement of an IUD, but this is rare. All women should consider not smoking when using hormonal birth control. Though the initial cost of an IUD is relatively high, it may be cost effective over time.

* The Affordable Care Act requires insurance companies to cover with no co-pay any FDA-approved contraceptive method prescribed by your doctor, including barrier methods, hormonal methods, implanted methods, emergency contraception, female sterilization and patient education and counseling. These estimated costs apply to women who do not have insurance coverage or who work for a "religious employer," who may be exempt from providing contraceptive coverage. For details about what your insurance covers, contact your benefits coordinator or health insurance provider.