111811 teen pregnancy
The National Teen Pregnancy Awareness Month event in Times Square on May 3, 2011 in New York City. - 

Jeremy Hobson: The Centers for Disease Control and Prevention is reporting this morning that teenage girls in the U.S. are having fewer babies than ever before. The teenage birth rate has hit its lowest level since 1940, when the government started keeping track.

Marketplace's Amy Scott reports.

Amy Scott: Not so long ago, demographers were worried about rising teen birth rates, egged on by celebrity moms like Bristol Palin and the movie Juno.

Juno: There it is. That little pink plus sign is so unholy.

So what happened in the space of a few years?

Bill Albert: Less sex and more contraception.

That's Bill Albert with the National Campaign to Prevent Teen and Unplanned Pregnancy. He says the rise in teen birth rates in 2006 and 2007 was a blip in a long period of declines. He credits better sex education for last year's big drop -- and the bad economy.

Albert: I'm not here to suggest that teens are checking the Dow Jones average before they hop into the sack. But they're not immune to the business cycle either.

Albert say teens watching grownups struggle may think better of starting families. And adults are having fewer babies too -- birth rates for all age groups fell -- except for women in their early 40s, who don't have the luxury of waiting for the economy to improve.

I'm Amy Scott for Marketplace.

Follow Amy Scott at @amyreports