Jaycee Dugard

Jaycee Dugard says she didn't know she was pregnant when she gave birth to her first child.

"I didn't know I was in labor," she told Diane Sawyer on Primetime. "I was still ... locked at that time. Just scared."

Dugard, who was kidnapped at age 11 in 1991 and held in captivity for 18 years by Phillip and Nancy Garrido, got pregnant at 13, but she didn't understand sex or why she was gaining weight. In her memoir, A Stolen Life, she writes that the Garridos told her she was pregnant and gave her birthing videos to watch to prepare for labor since there would be no medical care. She gave birth to a daughter in 1994 in the Garridos' backyard.

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"[It was] very painful, then I saw her — she was beautiful," Dugard said. "I felt like I wasn't alone anymore. I had somebody that was mine. I wasn't alone and I knew I could never let anything happen to her. I didn't know how I was going to do that but I did."

Dugard gave birth to a second daughter three years later and, despite only attending school through the fifth grade, taught her children.

"There's a switch that I had to shut off," Dugard said. "You can't imagine being kidnapped and raped, you know? ... You do what you have to do to survive."

Dugard's full Primetime interview airs Sunday at 9/8c. Watch a clip below: