The teen birth rate in the United States reached an all-time low last year, the Centers for Disease Control and Prevention reported on Thursday.

One expert said the bad economy and teen pregnancy reality shows may have played a role in the decline.

There were 34.3 births per 1,000 teenagers aged 15-19 in 2010 - a 9 percent drop from the prior year and the lowest rate in the nearly 70 years data has been collected, the CDC said.

The CDC also reported the first drop in the rate of caesarean deliveries since 1996. That rate declined to 32.8 in 2010 from 32.9 in 2009.

The birth rate for teens has gone down for the last three years and in 17 out of the last 19 years, the agency said. In 2010, birth rates also dropped to historic lows for mothers aged 10-14.

“It was really a dramatic one-year decrease,” said Bill Albert, spokesman for the National Campaign to Prevent Teen and Unplanned Pregnancy, a nonprofit based in Washington.

Teen pregnancy rates have dropped 44 percent since peaking in 1991, Albert told Reuters.

“That is extraordinary progress on an issue that many consider intractable and inevitable,” Albert said.

He attributed the drop to increased sex education in schools and the slow economy, which he believes has a sobering effect even on teens.

The reality television shows about teen pregnancy also may have contributed to the decline, he said. The shows provide young viewers with a “sobering look at the reality of being a parent,” he said.

The total number of births in the United States declined as well in 2010, dropping 3 percent to about 4 million from about 4.1 million, the CDC said.

Birth rates for unmarried mothers declined to 47.7 per 1,000 unmarried mothers in 2010, down from 49.9 the year before. The percentage of births to unmarried mothers lowered slightly to 40.8 percent from 41 percent, the CDC said.

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By David Beasley

ATLANTA