That comes from a new Guttmacher Institute report, which looks at rates of unintended pregnancies across the country. It finds that, in 2008, most pregnancies in 31 states were unintended, meaning they were either mistimed or unwanted.
The Guttmacher report shows that, generally, states in the South, Southwest and with larger urban areas tend to have higher rates of unintended pregnancies. More unintended pregnancies were mistimed than unwanted.
The District of Columbia has both the highest percentage of pregnancies that are unintended, and the highest rate of unintended pregnancies (80 unintended pregnancies per 1,000 women ages 15-44). This likely has a lot to do with the fact that, unlike any other jurisdiction, the District is pretty much a completely urban jurisdiction.
When the District is excluded, Delaware is the state with the highest rate of unintended pregnancies, followed by California, Mississippi, Louisiana and New York. New Hampshire has the lowest rate of unintended pregnancies: 31 per 1,000 women ages 15-44).
You can see some of the trends in this map that Guttmacher put together, showing the rate of unintended pregnancies for each state.