More US women are taking the "morning-after" pill, but generally just once, according to the government's first report on how the emergency contraception drug has been used since regulators eased access to it in 2006.
About 11 percent of sexually active women, or 5.8 million, used the pill between 2006 and 2010, compared to about 4 percent in 2002, the Centers for Disease Control and Prevention said in its report released on Thursday.
Among those who used the pill during those four years, 59 percent said they took it just once, while 24 percent said they used it twice, the report said. Seventeen percent said they used it three times or more.
Emergency contraception has been available by prescription in the United States since 1999. One version of the morning-after pill, known as Plan B, has stirred the most political controversy.
Plan B, much like regular birth control, stops pregnancy by blocking the release of a woman's egg, or it may prevent fertilization or implantation in the uterus. But it must be taken within days after intercourse to work.
The US Food and Drug Administration approved sales of Plan B to adult women without a prescription in 2006 after years of contentious debate. It later loosened the restriction to include 17-year-olds.
Women's health groups lauded the move as a way to prevent unwanted pregnancies. But conservatives warned it could lead to promiscuity, especially among youth, and more sexual assaults.
Amy Allina of the National Women's Health Network said CDC's findings show morning-after pills are not replacing conventional birth control methods for most women, although "there are some for whom it's clearly not a one-time thing."
Activists are still pressing for over-the-counter access and no age restrictions.
The pill is sold by Teva Pharmaceutical Industries Ltd as Plan B. It also is available as a generic. In 2010 the FDA approved another emergency contraceptive called ella, a prescription drug now owned by Actavis Inc.
CDC's findings showed the reasons for emergency contraception use varied depending on race and education levels.
Hispanics and blacks were more likely than whites to report using the drug after unprotected sex. More white women said they used it because they were worried their other birth control method had failed, CDC said.
Those with at least some college education were more likely to use the pill than those with a high school education or less, according to the report, which is based on data from the CDC's