Using another measure that calculates frequency of unintended pregnancies, the analysis by the nonprofit Guttmacher Institute found the highest rates of unintended pregnancy were in the South, Southwest and in states with large urban populations. Highest was Mississippi with 69 per 1,000 women ages 15-44; lowest was New Hampshire, with 36 per 1,000.

"There are many, many reasons why people don't plan ahead, even when it's such a crucial decision," says Claire Brindis, director of the Bixby Center for Global Reproductive Health at the University of California-San Francisco, who was not involved in the analysis.

Brindis says difficulty in finding family-planning services and lack of access to birth control contribute to the high numbers of unintended pregnancies. There is "a very strong denial factor — (people think) 'this won't happen to me,'" she says. Read rest of article