The Center for Disease Control and Prevention reports that 37 percent of births in the U.S. were unintended at the time of conception.
It's a number that has not changed since 1982.
Among women having unintended births, 60 percent did not use contraception and 36 percent of those women didn't think they could get pregnant.
If women in the U.S. avoided unwanted pregnancies the number of births would drop by more than 580 thousand annually.
Experts say keeping track of these births is important because they can relate to adverse social, economic, and health outcomes for the mother and the child.