Even at an all-time low, the U.S. teen pregnancy rate is still the highest among developed countries.

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Teens are notorious for spurning adults’ advice, but when it comes to getting pregnant, their refusal to listen is more than merely annoying: it’s become a public health problem.

A report released Thursday by The Centers for Disease Control and Prevention (CDC) surveyed close to 5,000 girls in 19 states who got pregnant unintentionally and subsequently gave birth between 2004 and 2008. Half had not used birth control and a third explained their reasoning by saying they didn’t think they could get pregnant. Go figure.

What’s behind their curious calculations is pretty murky because the CDC didn’t ask them to explain their thinking. But previous research has discovered that girls who get pregnant in their teens harbor a number of misconceptions about their menstrual cycles. Some thought there was no way to get pregnant at the same time they lost their virginity, while others had an incorrect understanding of how ovulation works and at what point in the month they were most fertile. Still others thought they couldn’t get pregnant at all, although why they believed that is unclear.

In fact, research conducted by the Washington, D.C.-based National Campaign to Prevent Teen and Unplanned Pregnancy found that 40% of respondents said contraception wasn’t important because they thought they would get pregnant regardless. So while the CDC study authors expressed surprise at the number of teens not using birth control, Bill Albert, spokesman for the Campaign, barely blinked.

“Not to get too biological here, but the only teen girls getting pregnant are the ones who are having sex and not using contraception consistently, carefully or at all,” he says.

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What may be even more concerning is the percentage — almost 25% — of girls who said they didn’t use birth control because their partners pressured them not to. Just 13% of girls said they shunned birth control because it wasn’t easily accessible. Of those girls who shared what type of birth control they used, about 20% said they relied on the pill or a hormonal patch; 24% used condoms.

The new statistics are being released as the overall teen birth rate is at its lowest point ever. Although the U.S. still boasts the highest teen pregnancy rate of any developed nation, the national teen birth rate dropped in 2010 to 34.3 births per 1,000 girls aged 15 to 19, down from 37.9 the year before. That marked a pretty meaningful decrease from 1991, when the teen birth rate hit a high of 61.8. The significant decline — what Albert refers to as a “great American success story” — indicates that many teens must be getting the message and are actively trying to prevent pregnancy.

“The magic formula of less sex and more contraception is responsible for this great good news,” said Sarah Brown, CEO of The Campaign, in a statement about the decline. “Teens are being more careful for a number of reasons, including the recession, more media attention to this issue — including the ‘16 and Pregnant/Teen Mom’ effect — and more attention to and investment in evidence-based programs. But at the end of the day, the thanks and admiration go to teens themselves.”

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In 2010, I wrote about the two MTV shows to which Brown refers and how — instead of glamorizing teen pregnancy — they actually deter it. As Albert summed it up then: “This might be the best teen pregnancy public service announcement ever made.”

The story pulled from the Campaign’s website:

“Although research has documented an association between exposure to sexual content on television and teen pregnancy, little research has been conducted to better understand how media might also have positive effects. Can the media, for example, decrease risky sexual behavior and promote healthier decisions among teens?” They decided to commission a study to find out. What they concluded, says Albert, is that “while MTV is not in the teen pregnancy prevention business, we firmly believe they have developed two shows that are probably among the most powerful interventions you’re likely to see.”

Teen pregnancy is an important public health marker because babies born to teen moms are more likely to be born prematurely, weigh less and endure other complications. Meanwhile, teen moms are far more likely than older moms to experience the social cold shoulder.

To illustrate that, one Washington state teen, Gabby Rodriguez, recently highlighted the way people responded to her as her pregnancy progressed through her senior year of high school. She had staged the whole thing, duping even her family — though obviously not her boyfriend — as part of an elaborate senior project/social experiment that tackled the effect of stereotypes and rumors. Rodriguez documented people’s attitudes as she moved from loose-fitting clothes to a faux baby bump.

Now a freshman in college, Rodriguez has written a book, The Pregnancy Project, about her experience, and is the subject of a Lifetime movie of the same name that is scheduled to air Jan. 28. As part of a publicity blitz, she’ll appear on the Dr. Phil show, speak at the New York Public Library and grace the pages of People magazine. Perhaps most significantly — at least in terms of making a statement about teen pregnancy to her target audience — is her planned four-page spread in the February issue of Seventeen magazine.