Story highlights The number of births in the US rose 1% in 2014, the first increase since 2007

The reproductive rebound was driven by women in their thirties and forties who may be responding to the economic rebound

The rate of teen births dropped to 24.2 for 1,000 teens, which is an all-time low

(CNN) The number of births in the United States went up last year for the first time since 2007, according to an annual report by the CDC National Center for Health Statistics. The report found that there were 62.9 births for every 1,000 women between the ages of 15 and 44, which represents an increase of 1% over the birth rate in 2013.

The spike was driven by women in their 30s and early 40s, who had 3% and 2% more births, respectively, than in the previous year. For women in their 30s, the birth rates were 100.8 per 1,000 women age 30 to 34 and 50.9 per 1,000 women age 35 to 39. In contrast, the birth rate among teens 15 to 19, which has been waning since 1991, plummeted 9% since 2013. It was 24.2 per 1,000 teens in 2014. The rate among women in their early 20s also dropped by 2%.

"The births to older women was enough to offset the decline in teen birth rate and you see this overall increase," said Brady E. Hamilton, a statistician and demographer at the National Center for Health Statistics and lead author of the study.

"In regards to the older women, this is kind of a continuation of a trend, but the decline in teens 15 to 19 really shocked me; 9% is really phenomenal," Hamilton said.

The birth rate among teens has gone down 61% since 1991. But the rate of decline has picked up speed in the last seven years, dropping 7% annually between 2007 and 2013 and now 9% in the last year.

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