As many as 11% of U.S. women ages 15-44 who have ever had sexual intercourse
have used a "morning after" pill at least once, according to the first federal report on emergency contraception, out Thursday.
That's 5.8 million women -- and half say they used it because they feared their birth control method may have failed. The rest say they had unprotected sex.
The National Center for Health Statistics analysis is based on responses collected through in-person interviews with 12,279 women from 2006-2010. Of those, 10,605 said they were sexually experienced.
The FDA approved emergency contraceptive pills in 1998 for use up to five days after intercourse. But experts say there are plenty of obstacles to widespread use.