In 2010, more than half of all pregnancies were unintended in 28 states; in the remainder of states, a minimum of 36% of pregnancies were unintended, according to "Unintended Pregnancy Rates at the State Level: Estimates for 2010 and Trends Since 2002," by Kathryn Kost. In most states, unintended pregnancy rates were within the range of 40 to 55 per 1,000 women aged 15–44; the states with the highest unintended pregnancy rates were Delaware (62), Hawaii and New York (61 each), and the lowest rate was in New Hampshire (32). Unintended pregnancy rates were generally highest in the South (Georgia, Florida, Louisiana, Mississippi, Virginia) and Southwest (Texas, New Mexico), and in densely populated states (Delaware, Maryland, New Jersey, New York).

This analysis looked at trends between 2002 and 2010. Across the decade (2002–2010), unintended pregnancy rates fell 5% or more in 18 states and rose 5% or more in four states. For the remaining 12 states with data available in both 2002 and 2010, unintended pregnancy rates remained mostly unchanged. However, trends in the first half of the decade were markedly different than those in the second half. Of the 33 states with data available for 2002 and 2006, only Michigan experienced a rate decrease of 5% or more during this period. Sixteen states experienced increases of 5% or more, and the remaining 16 states experienced little to no change. That trend reversed in the latter half of the decade. Between 2006 and 2010, 28 of the 41 states with data available for both years experienced rate decreases of 5% or more. Only one state, West Virginia, experienced an increase of 5% or more. The remaining 12 states experienced little to no change.

"The decline in unintended pregnancy rates in a majority of states since 2006 is a positive development," says study author Kathryn Kost. "However, rates remain twice as high in some southern and densely-populated states compared with those in other states—a variation that likely reflects differences in demographic characteristics and socioeconomic conditions across states."

National data on contraceptive use indicates that the use of the most effective available methods has increased, which could also have played a role in recent decreases in unintended pregnancy rates. Indeed, three states that conducted significant campaigns to increase use of long-acting methods—Colorado, Iowa and Missouri—all saw double-digit percentage declines in their unintended pregnancy rates.

In addition, previous Guttmacher research estimated that, in 2010, publicly funded family planning services helped avert 2.2 million unintended pregnancies that would have resulted in more than 1.1 million unplanned births and 760,000 abortions.

"Publicly funded family planning centers play a critical role in helping many women avoid unintended pregnancy," says Guttmacher senior public policy associate Adam Sonfield. "Considering that nearly half of all pregnancies in the United States are unintended, we simply can’t afford not to invest in publicly funded family planning."