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Birth Control Health Center

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IUD Beats Pill at Preventing Pregnancy

Birth Control Pill's Risk of Failure Is 20 Times More Than That of IUDs, Implants

How They Work continued...

An IUD is a small "T" shaped device that is inserted into the uterus by a health care provider. It works by stopping sperm from making it through the vagina and uterus to fertilize an egg.

There are two types of IUDs available in the U.S., the Mirena hormonal IUD and ParaGard copper IUD. Both are more than 99% effective at preventing pregnancy for five to 10 years, depending on the device.

If taken exactly as directed, birth control pills are also more than 99% effective at preventing pregnancy.

But in reality, few women remember to take the pills at the same time every day to achieve these optimum results. The yearly failure rate with typical use is estimated to be 9%, but with younger women and high-risk groups the failure rate increases.

"There are also a lot of other barriers like getting refills, prescription renewals, and insurance coverage that comes and goes," says Sarah J. Betstadt, MD, MPH, assistant professor of obstetrics and gynecology at the University of Rochester. She was not involved in the study.

IUD Beats the Pill

Researchers say this is the first large study to compare the failure rate or number of unplanned pregnancies between users of IUDs or implants and short-term contraceptives, including birth control pills, patches, vaginal rings, and birth control shots.

After an initial consultation about birth control options, researchers provided 7,486 women of reproductive age with their choice of contraception free of charge.

During three years of follow-up, 334 unplanned pregnancies occurred. Of these, 156 pregnancies were due to failure of contraception provided during the study. The remaining unplanned pregnancies were due to failure of other forms of contraception not included in this study, such as condoms and withdrawal.

Researchers found that 133 women using pills, the patch, or ring experienced an unplanned pregnancy compared with 21 women who used IUDs or implants. Two women used birth control shots.

In addition, the risk of unplanned pregnancies among young women under age 21 using birth control pills, patch, or ring methods was twice as high as the risk among older women. The rates of unplanned pregnancy were similar between women using birth control shots and those using IUD or implant, regardless of age.

The results appear in the New England Journal of Medicine.

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