The number of babies born to teens and some women in their 20s hit new record lows in 2011, show federal data released Wednesday. The numbers suggest the continuing decline in births could be more than just the lingering effect of recession.

The number of U.S. births has been dropping since 2007, when they peaked at 4.3 million, just before the worst economic downturn since the Depression. But now, substantial declines in just one year among certain segments of women suggest a deeper and potentially longer-lasting change in childbearing.

"Most demographers were expecting a mini-baby boom right now," says demographer Sam Sturgeon of Taylorsville, Utah, president of Demographic Intelligence, a consulting company in Charlottesville, Va. "We anticipated that because the number of women of prime childbearing age has gone up. We were looking at what would have been the grandchildren of the baby boomers."

The boom "never materialized," says Sturgeon.He adds fertility rates usually rise within a year or two of a recession's end.

Instead, show 2011 stats from the National Center for Health Statistics:

-- The number of births to teens 15-19 dropped 10%, to 329,797, marking the fewest teen births since 1946. Teen birth rates also fell 8% to 31.3 births per 1,000, the lowest recorded since 1940. The rate has declined more than 3% a year since 1991.

-- The number of births to women ages 20-24 declined 3% from 2010 to 2011, and the birth rate dropped 5%. The birth rate was 85.3 births per 1,000, the lowest ever recorded in the USA, the report notes.

-- For those 25-29, the birth rate, 107.2 births per 1,000 women, was the lowest since 1976.

Although the recession may well have postponed starting a family for women in their 20s, the economy typically doesn't affect teens, whose births are largely unintended and unplanned, demographers say.

It may be a year or two before experts can determine what's really going on, says Steven Martin, an assistant professor of sociology at Christopher Newport University in Newport News, Va.

"It is hard to tell whether this is movement towards a long-term trend of lower fertility or the tail end of the fertility effect of a major recession," he says. "Reading all those trends together, it could indicate the United States is continuing to move towards a later birth pattern," similar to other developed countries.

The federal report notes that the pace of decline in the teen birth rate has accelerated since 2007, and since then, there's been a 25% drop. The all-time high teen birth rate was in 1957, 96.3 births per 1,000 teens.

For unmarried women, birth numbers and birth rates also declined from 2010 to 2011. The total number of births to unmarried women declined about 2%. In 2011, the non-marital birth rate dipped 3% in a year. Since 2008, it has dropped 11%.

The new data show that the rate for first births is also down, from 25.9 per 1,000 women 15-44 to 25.4 per 1,000.

"It means that -- at least in 2011 -- the rate of people starting families went down 2%. And it was the lowest ever recorded," says demographer Stephanie Ventura, co-author of the report. "It's an important measure because it signifies the beginning of childbearing."

The data suggests that women are putting off having the first child, Sturgeon says.

"It's your younger mothers that are delaying," he adds. "Is this going to become the new norm? The average age at first birth has been ticking up over the last couple of years. Is that a permanent change? I don't know."

USA Today