Health officials say birth rates for America's teens and young women hit new lows last year. The U.S. birth rate dropped for the third straight year, with declines for most ages and all races, according to a federal report released Thursday. Teens and women in their early 20s had the most dramatic dip to the lowest rates since record-keeping began in the 1940s. Experts suspect the economy has driven down birth rates. "I don't think there's any doubt now that it was the recession. It could not be anything else," said Carl Haub, a demographer with the Population Reference Bureau, a Washington, D.C.-based research organization.