Federal data shows a big decline in U.S. birth rates, and it could have less to do with the economy.

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The number of births to teens and women in their 20's fell eight and ten percent, marking the fewest births since the 1940's. For women 25-29, the birth rate was the lowest its been in 30 years.

"We know that the economy plays a significant role in the decline in birth rates, but its also important to know that some of these are births that women are putting off, holding off until they get in a better economic situation" said Brady Hamilton at the National Center for Health Statistics.

"At the end of the recession, most were expecting a mini baby-boom as the economy started to pick up and that really didn't happen" he added.

However, Hamilton says the economy typically doesn't affect teen birth rates.

"That's not something that would have anything to do with a reason teen birth rates are dropping."

The numbers could indicate women's move towards a later birth pattern.

"Women could be putting off having their first child" said Hamilton. "It could suggest a big change in child-bearing, a lot of women are waiting these days to have kids."

He says its hard to tell if this will be part of the new norm.

"The average age women are having their first child has been increasing, so could this be a more permanent change...we will have to wait and see."