Sarah Palin on Bristol Pregnancy: 'I Was Shocked'

In an interview with Barbara Walters, Sarah Palin said that she did not know her daughter Bristol was sexually active before learning of her pregnancy.

"That's why I was shocked," Palin said. "Truthfully, we were devastated."

Palin announced that Bristol, then a high school senior, was pregnant in September 2008 -- a few days after she accepted the offer to become the Republican vice presidential nominee.

Bristol, 19, gave birth to son Tripp in December.

Walters sat down with the former vice presidential candidate and Alaska governor for a five-part series of ABC News interviews to begin airing on "Good Morning America" Nov. 17, the morning her highly anticipated book, "Going Rogue: An American Life" is released.

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As part of the wide-ranging interview, Walters asked Palin about her public life as governor of Alaska and the 2008 GOP vice presidential nominee, as well as her private life and presidential aspirations.

Palin's 15-year-old daughter Willow weighed in, telling Walters it "would be cool" to see her mom become president.

Watch Barbara Walters' interview with Sarah Palin starting Tuesday on "Good Morning America", "World News" and "Nightline", more Wednesday on "Good Morning America," and the full interview on "20/20" Friday, Nov. 20 at 10 p.m. ET.