Diane Sawyer (left) and Jaycee Dugard
Ida Mae Astute/ABC; Nick Stern/Redthinkmedia/WENN
Three years into her captivity
, Jaycee Dugard went into labor with her first child – a frightening experience compounded by the fact that she didn't understand what was happening to her.
"I didn't know I was in labor," Dugard, now 31, tells ABC News's Diane Sawyer
in an exclusive, two-hour interview to air on Sunday's Primetime
. "I was still … locked [in] at the time. Just scared."
Dugard lost 18 years of her life
when she was kidnapped
in 1991 at age 11 by Phillip and Nancy Garrido.
In addition to the Sawyer interview, she has published a detailed story of her ordeal, the book A Stolen Life
, excerpts from which
appear exclusively in this week's PEOPLE.
In the book, she writes that she didn't understand sex before she was taken prisoner. Giving birth, she says, was extremely painful, especially since she realized she would be receiving no medical care.
But, she tells Sawyer, when her first daughter arrived, "she was beautiful. I felt like I wasn't alone anymore. [I] had somebody else who was mine. I wasn't alone."
Dugard gave birth to another girl in 1997, and she educated her children, creating a school while held captive despite her fifth grade education.
"There's a switch that I had to shut off," Dugard tells Sawyer in the interview. "You can't imagine being kidnapped and raped, you know? … You do what you have to do to survive."
For eight pages of exclusive excerpts from
A Stolen Life and never-before-seen photos, pick up this week's issue of PEOPLE, on newsstands Friday