NEW YORK — Teen births fell again in the United States in 2010 with the highest rate once more in Mississippi, according to a new government report.

Nearly every state saw a decline in teen births from 2007 to 2010, with the biggest drop in Arizona at 29 percent. Rates stayed about the same in three states: Montana, North Dakota and West Virginia.

The Centers for Disease Control and Prevention previously reported that U.S. births by mothers of all ages had dropped in 2010 for the third straight year. Experts think the economy is a factor.

The rate for teenage moms reached its lowest point since record-keeping began in 1940. The rate fell 9 percent to about 34 per 1,000 girls ages 15 through 19. The decline was seen among all racial and ethnic groups.

The CDC report released today focused on state figures. The authors say the teen declines have been attributed to pregnancy prevention efforts. They note that a recent government survey showed more use of contraception by teens.

Even as it leads the nation with 55 teen births per 1,000 girls, Mississippi’s rate has been falling like everywhere else. It dropped 21 percent over three years. New Hampshire has the lowest teen birth rate at just under 16.

Since 1991, the overall teen rate has dropped by 44 percent. Without that decline, the authors calculated, there would have been 3.4 million more babies born to girls by 2010.