Early data for 2012 is not yet available, and it's too soon to guess whether the birth decline will change, said the CDC's Stephanie Ventura, one of the study's authors.
Highlights of the report include:
—The birth rate for single women fell for the third straight year, dropping by 3 percent from 2010 to 2011. The birth rate for married women, however, rose 1 percent. In most cases, married women are older and more financially secure.
—The birth rate for Hispanic women dropped a whopping 6 percent. But it declined only 2 percent for black women, stayed the same for whites and actually rose a bit for Asian-American and Pacific Islanders.
—Birth rates fell again for women in their early 20s, down 5 percent from 2010 — the lowest mark for women in that age group since 1940, when comprehensive national birth records were first compiled. For women in their late 20s, birth rates fell 1 percent.
—But birth rates held steady for women in their early 30s, and rose for moms ages 35 and older. Experts say that's not surprising: Older women generally have better jobs or financial security, and are more sensitive to the ticking away of their biological clocks.
—Birth rates for teen moms have been falling since 1991 and hit another historic low. The number of teen births last year — about 330,000 — was the fewest in one year since 1946. The teen birth rate fell 8 percent, and at 31 per 1,000 girls ages 15 through 19 was the lowest recorded in more than seven decades.
"The continued decline in the teen birth rates is astounding," said John Santelli, a Columbia University professor of population and family health.
Did the economy have anything to do with a drop in teen births?
Yes, indirectly, Santelli said. Teenagers watch the struggles and decisions that older sisters and older girlfriends are making, and what they see influences their thinking about sex and birth control, he said.