What's Behind the Mysterious Drop in Teen Pregnancy?

Teen sex rates have fallen rapidly since the world met Bristol Palin. Photo via Wikimedia Commons 

Here's some good news: American teens are finally figuring out how to not have babies. According to new numbers released by the Centers for Disease Control and Prevention this week, the US teen birthrate fell to its lowest point since 1940 last year, with 277,749 babies born to mothers under 20. That means that there were 26.6 births for every 1,000 teen girls in the US in 2013, down 72 percent from an all-time high in 1957.

While we've known for a few years now that teen birth rates have been falling, the new CDC data illustrates just how precipitous the drop has been. According to the report, the teen birth rate fell 52 percent between 1991 and 2012, with the number of teen births falling across age groups and ethnicities, and in all 50 states. In that period, the steepest declines were seen among black teens and Asian Americans, with the teen birth rate falling 83 percent and 64 percent, respectively, among those groups. More recently, the declines have been steeper and faster, with the number of teen births falling a full 29 percent between 2007 and 2012. In that period, too, the declines were seen across regions and groups, with the steepest decline recorded among Latina teens (39 percent).

Image via CDC

The numbers echo a report published earlier this year by the Guttmacher Institute, which found steep declines in teen pregnancy between 1991 and 2010, the last year for which data was available. According to that data, just six percent of women between the ages of 15 and 19 got pregnant in 2010, a 51 percent drop from 1990 and a 15 percent decrease from 2008 alone. Combined with the new CDC numbers, it seems that not only are fewer teen girls having babies, fewer are getting pregnant in the first place.

Obviously, this is a very good thing. The majority of teen pregnancies are not planned, and teen mothers are significantly more likely than older mothers to have dropped out of high school, live below the poverty line, receive food stamps and Medicaid benefits, and to not receive assistance from the fathers of their children. All of this makes teen births very expensive for the American taxpayer: According to the CDC, the average child born to a teen mother costs the taxpayer an estimated $1,700 per year until age 15; CDC researchers guess that the drop in teen pregnancy saved taxpayers $12 billion in 2010 alone.

The problem is, no one can explain why this is happening. Clearly some teenage girls have figured out a way to avoid getting pregnant. But what exactly it is that they are doing-and why-remains a mystery.

According to the CDC report, at least part of the reason for the decline stems from the fact that fewer teens are having sex, and from the more widespread use of birth control among teens who are sexually active. Data from the CDC's National Survey of Family Growth showsthat the number of teenage girls who describe themselves as "sexually experienced" has been going down for the past two decades, and that a growing number of teens who are having sex report using some form of birth control, and often two forms of birth control. Researchers point out that these numbers correspond to a period of implement.

But as I wrote back in May, this explanation doesn't account for the unprecedented drop-off in teen births over the last five years. For one, according to data from the federal government's Youth Risk Behavior Surveillance System, the rate of teen sexual activity has remained relatively level since 2007, while the number of teen births (and teen pregnancies) has plummeted. And while contraception use has increased among some teens-the availability of IUDs and Plan B, in particular, seem to have had an affect on birth rates-the federal data shows that since 2007, more teens are choosing not to use any contraception at all. That number is echoed by federal STD statistics, which show that half of new infections in the US are contracted by people under age 25, and that girls ages 15-19 have the largest number of reported cases of gonorrhea and chlamydia.

"There seems to be an unsolvable mystery here," Bill Albert, the chief program officer for the National Campaign to Prevent Teen and Unplanned Pregnancies, told me. "Teen sex has gone down, but it has leveled off, contraceptive use continues to creep up a little bit. But pregnancy rates have fallen off the charts. And yet the STD rates remain quite high."

So what exactly is it that is preventing teen girls getting knocked up? Maybe it's the recession. Or maybe teen boys are just pulling out. Maybe its some combination of factors-a "perfect storm," as Vox's Sarah Kliff suggestedin a lengthy piece on the subject this week. Whatever it is, finding the answer could unlock the secret to helping the too-high number of teen girls that are still getting pregnant. Because despite the positive trend lines, the US teen birth rate remains one of the highest among other developed nations, ranking 29 on a list of 31 countries highlighted in the CDC report.

"When we talk about all of this good news, we do have to temper it a bit with a glass half-empty interpretation," Albert said.  "The wrong message to take from the new data is that we can pack up our tents and go home. It's not like we found a vaccination."