June 16, 2003 -- It is widely known as the "morning-after pill," but new research confirms that emergency contraception reliably prevents pregnancy even when taken as long as five days after having sex.
Researchers say the current three-day cutoff for using emergency contraception is unnecessary and is not supported by the scientific evidence.
"The 72-hour window was completely arbitrary because that is what the first studies used," researcher James Trussell, PhD, tells WebMD. "This is just the latest study to suggest that this window can be extended for two more days."
Similar Pregnancy Rates
Trussell and colleagues followed 111 women who took emergency contraception between 72 and 120 hours after having unprotected sex. Pregnancy rates were compared to 675 women who took emergency contraception within three days.
The two groups had similar pregnancy rates -- roughly 2% for women who took the emergency contraception within three days and 3% for those took it three to five days after sex.
The researchers do say that the small number of women in their study could have underestimated the difference in pregnancies between the two groups of women. Their findings are published in the June issue of the journal Obstetrics and Gynecology.
The idea of preventing pregnancy by taking larger-than-normal doses of birth control pills soon after sex has been around for years. But newly released surveys suggest that only 6% of women in the U.S. have ever used emergency contraception. Experts say many women still do not know about the option or they confuse it with the controversial abortion pill RU-486.
It's Not RU-486
Unlike RU-486, the two emergency contraceptives available in the U.S. -- Plan B and Preven -- do not interrupt established pregnancies. They are believed to work by preventing either ovulation or implantation of the embryo.
Trussell, who directs Princeton University's Office of Population Research, says emergency contraception has been slow to catch on in the U.S, in part because it is still too difficult to get.
But four states now allow pharmacists to dispense emergency contraception pills, and the FDA is considering a request to make Plan B available over the counter. More than 60 health organizations and women's groups support the move, including the American College of Obstetrics and Gynecology and the American Medical Association.
Reproductive health advocate Kirsten Moore agrees that lack of knowledge and access are major obstacles to the acceptance of emergency contraception. She says it is important for doctors to discuss emergency contraception with appropriate women during annual exams and to offer the pills to their patients. Moore is president of the Reproductive Health Technologies Project, a not-for-profit educational group devoted to expanding birth control options.
"Even though these pills are effective for several days, the emphasis should be on taking them as soon as possible after having sex," Moore tells WebMD. "The best way to ensure this happens is if they are already in a woman's medicine cabinet."