Jaycee Dugard describes 18 years in captivity

California resident Jaycee Dugard,kidnapped in 1991 and held captive for nearly two decades, talked through tears about both the pain and determination she felt as she gave birth to her captor's child in his backyard while she was still just a girl herself.

Dugard was clear and composed throughout theinterview with ABC News' Diane Sawyer on Primetime that aired Sunday night, but grew emotional when she talked about seeing the first of two girls fathered by Phillip Garrido.

When Sawyer asked how old she was at the time of the birth in the San Francisco Bay Area city of Antioch, she said "14" with a small, incredulous laugh and a shake of her head.

'I felt like I wasn't alone anymore.' Jaycee Dugardon giving birth to herdaughter

"It was very painful," said Dugard, now 31, as tears welled in her eyes. "She was beautiful. I felt like I wasn't alone anymore."

She said she didn't know how she could protect the child, but said "I knew I could never let anything happen to her."

Dugard appeared younger than her 31 years as she talked to Sawyer on a couch and on a porch at her California home. The blond hair she had in now-familiar photographs from her childhood is now reddish-brown, and she wore a red sweater and a necklace with a pinecone charm on it, representing the last thing she touched before her 18-year captivity.

Captor sentenced to 431 years to life

The interview came on the eve of Dugard's memoir about her time in captivity, A Stolen Life, which will be released this week.

Dugard told Sawyer there was "a switch" she had to shut off to emotionally survive her rape and imprisonment.

She described walking to the school bus stop on the day of a fifth-grade field trip and being zapped with a stun gun on a South Lake Tahoe street at age 11.

She said she heard Garrido laughing and telling his wife Nancy Garrido, "I can't believe we got away with it," calling the moment "the most horrible moment in your life, times 10."

"I lost control of my bladder," Dugard told Sawyer in one of many moments in the interview where she appeared astounded she was talking about herself. "I wasn't even embarrassed. There was no time to be embarrassed."

Dugard said she tried to hold in her tears because of her cuffed hands.

"I tried not to cry because I couldn't wipe them away," she said, "and then they get itchy."

She recalled the soundproof door of the backyard studio that Garrido shut and locked each time he left her.

"I can still hear it, consciously, when I'm awake," Dugard said. "Some sounds and smells just don't leave you."

Phillip Garrido, 60, a serial sex offender, was given the maximum possible sentence of 431 years to life in prison last month after pleading guilty to kidnapping and 13 sexual assault charges, including rape and committing lewd acts captured on video.

His plea was part of a deal with prosecutors that saw Nancy Garrido, 55, sentenced to 36 years to life after pleading guilty to kidnapping and rape.