Senior Year, a Quick Choice...and a Big Surprise

June 23, 2009 -- They're well-to-do and they have a problem -- but they're not alone.

The family of Hannah, a high school senior in Yakima, Wash., is facing a quandary that more than 729,000 American families deal with every year: teen pregnancy. Even their very nice house in their very nice, sheltered orchard didn't keep Hannah, 18, safe. Neither did all her high school achievements.

"I was a homecoming king and queen with my boyfriend of three years," Hannah told "Primetime" in an interview in her hometown. "I was a cheerleader, I played volleyball, I was in a lot of school activities. I really was part of the school."

Last fall Hannah found out she was pregnant by her on-again, off-again boyfriend, Taylor. He was a B.M.O.C., a champion athlete. They were an all-star couple.

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"When I hear an auditorium cheer for Taylor ... You know, he deserves it," said Hannah. "He's worked really hard pretty much all his life to get where he is."

But all of that was derailed by a single moment. Hannah explained how it happened.

"I used to be on birth control," she said. "I just forgot to take it. Me and Taylor would break up and get back together so much it just messed up my period, so I stopped taking it. We used a condom every time until we were on a break and it was spur-of-the-moment. I did Plan B [emergency contraception] after that, but evidently it didn't work."

According to Mark Regnerus, an assistant professor of sociology at the University of Texas at Austin and author of "Sex & Religion in the Lives of American Teenagers," upper-middle class teens are more likely to use Plan B as a source of protection.

"It's not surprising that Plan B would be more popular among the upper-middle class," Regnerus said in a telephone interview. "They're a more strategic group of kids that have a strong orientation toward their future. I'd be willing to bet, however, that their use of it is not to replace contraception but to augment it, 'just to be safe.' That is, few such kids are consciously playing sexual Russian roulette… Plan B is for when they've 'messed up.'"

CLICK HERE to see photos of Hannah throughout her pregnancy.