Most striking in the new report were steep declines in Hispanic birth rates and a new low in teen births. Hispanics have been disproportionately affected by the flagging economy, experts say, and teen birth rates have been falling for 20 years.
Falling births is a relatively new phenomenon in this country. Births had been on the rise since the late 1990s and hit an all-time high of more than 4.3 million in 2007.
But fewer than 4 million births were counted last year, according to the new report. That's about 360,000 fewer kids born than in 2007 equivalent to the population of Miami proper. It's also the lowest number of births since 1998.
Among the people who study this sort of thing, the flagging economy has been seen as the primary explanation. The theory is that many women or couples who are out of work, underemployed or have other money problems feel they can't afford to start a family or add to it.
The economy officially was in a recession from December 2007 until June 2009. But well into 2011, polls show most Americans remained gloomy, citing anemic hiring, a depressed housing market and other factors.
The report by the Centers for Disease Control and Prevention is a first glimpse at 2011 birth certificate data from state health departments. More analysis comes later but officials don't expect the numbers to change much.
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.
"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.
"Teens tend to emulate young adults," Santelli said. "They are less influenced directly by the economy than by people."
Studies show that since 2007, larger percentages of sexually active teenage girls are using the pill and other effective birth control. Studies also show a small decline in the proportion of girls ages 15 through 17 who say they've had sex, Santelli noted.
The new birth report also noted a fourth straight decline in a calculation of how many children women have over their lifetimes, based on the birth rates of a given year.
A rate of a little more than 2 children per woman means each couple is helping keep the population stable. The U.S. rate last year was slightly below 1.9.
Countries with rates close to 1 such as Japan and Italy face future labor shortages and eroding tax bases as they fail to reproduce enough to take care of their aging elders.
Officials here aren't as worried.
The U.S. replacement rate is still close to 2. And it has dropped in the past and then bounced back up again, said Ventura, an official at the CDC's National Center for Health Statistics.
"And we haven't seen any studies that show couples want to have fewer children or no children," she added.
One more report highlight: The U.S. C-section rate may have finally peaked at just under 33 percent, the same level as last year.
Cesarean deliveries are sometimes medically necessary. But health officials have worried that many C-sections are done out of convenience or unwarranted caution, and in the 1980s set a goal of keeping the national rate at 15 percent
The C-section rate had been rising steadily since 1996, until it dropped slightly in 2010.
"It does suggest the upward trend may be halted," said Joyce Martin, a CDC epidemiologist who co-authored the new report. But CDC officials want a few more years of data before declaring victory, she added. =
Among report's highlights:
• 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.
• The birth rate for Latino women dropped a whopping 6 percent. But it declined only 2 percent for black women, stayed the same for whites and actually rose 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.
• Rates held for women in their early 30s, and rose for those ages 35 and older. Experts say that's not surprising: Older women generally have more 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.