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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
By
WebMD Health News
Reviewed by Louise Chang, MD

iud

May 23, 2012 -- Women using birth control pills may have a 20 times greater risk of an unplanned pregnancy than women using longer-acting forms of birth control like an intrauterine device (IUD) or implant, new research shows.

A major new study shows the failure rate of birth control pills and other short-term prescription contraceptives is much higher than previously thought, based on how women actually use them in real life.

Researchers say the results call for a major shift in how women and health care providers think about birth control options.

"In medicine, whether you have stroke, hypertension, or diabetes, if you have a medication that is 20-fold less effective, would you offer it as first-line choice?" says researcher Jeffrey Peipert, MD, of Washington University in St. Louis.

Birth control pills are currently the most commonly used reversible form of birth control in the U.S.

Only about 5.5% of American women who use contraception use IUDs, compared with much higher usage rates in other developed countries like the U.K. and France.

Removing the 'Oops' Factor

Researchers say unplanned pregnancies are a major public health issue. Unplanned pregnancies can have a negative impact on women's health and education as well as the health of newborns.

Previous studies have shown that about half of the estimated 3 million unplanned pregnancies each year in the U.S. are the result of contraceptive failure.

Although short- and long-term birth control methods work slightly differently in terms of preventing pregnancy, Peipert says the main reason behind the much lower failure rate for the IUD and implant is the removal of the "oops" factor.

"These methods are forgettable," Peipert tells WebMD. "You don't have to remember to take a pill, get a shot, or put in a ring. They remove human factor in terms of human error."

How They Work

Hormonal implants work by slowly releasing hormone to prevent the ovaries from releasing eggs. They are inserted under the skin of the upper arm and are effective for up to three years. They are available as Implanon and Nexplanon in the U.S.

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.

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