A new study confirms that long-acting forms of contraception such as intrauterine devices (IUDs) and implants are better than birth control pills and patches at preventing pregnancies, giving doctors new ammunition to recommend these methods.

The study, published Thursday in the New England Journal of Medicine, involved about 7,500 women in a project promoting long-acting birth control to reduce unintended pregnancies.

There are an estimated three million unplanned pregnancies a year in the US, often because of incorrect or inconsistent use of contraception, and about 1.2 million abortions, according to research cited with the study.

The Contraceptive Choice project is being run by researchers at Washington University School of Medicine in St. Louis. The study was funded by the Susan Thompson Buffett Foundation, a charity of Warren Buffett, chief executive of Berkshire Hathaway.

The study found that long-acting contraception is about 20 times more effective at preventing pregnancy than pills, patches or vaginal rings because those methods "wipe out the human error factor," said Jeffrey Peipert, a professor of obstetrics and gynecology at Washington University.

"IUDs and implants are more effective because women can forget about them after clinicians put the devices in place."

Failure rates for such methods are less than one percent but they require an office procedure and can cost patients several hundred dollars if not paid for by insurance, doctors said.

Hormonal implants are inserted under the skin of the upper arm and are effective for three years. IUDs are inserted into the uterus and last five or 10 years, depending on the type.

IUDs and implants can be removed if women want to try to become pregnant. Peipert said fertility returns immediately in most women.

Birth control pills are the most commonly used contraceptive in the US, but women need to take the pills daily for them to be fully effective.

Other studies have shown that many women -- especially teenagers -- miss two or more pills per menstrual cycle, which cuts the effectiveness at preventing pregnancy.

Read more: The Wall Street Journal

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