"Trig came early ... about five weeks early, and I was thinking it would be in that last month that I would be prepared enough in my own heart to be able to share with my kids the preparation that was gonna be necessary," she said. "I had written a letter to family and friends ... hadn't delivered it yet, though."
Palin said she wrote the letter "as if it were the words of our creator."
Was it presumptuous to write a letter in the name of God?
"I would do it again in a heartbeat," she said. "I do think that it was the most loving way to express my belief that God doesn't make any mistakes, and that Trig would be in our eyes perfect for our family."
Palin's daughters Piper and Willow agreed, saying they sometimes took care of their new brother.
"We all pitch in," said Willow. "We love him. He's the center of our world."
About five thousand children like Trig are born with Down syndrome every year in the United States. All are mentally challenged to varying degrees. They may face retardation, delayed language and slow motor development. Half of the babies born with Down each year suffer from congenital heart defects; Trig has a hole in his heart that may require surgery. So far, Palin said he can walk, but he has vision problems and, at 19 months, doesn't eat solid foods.
It wasn't long ago that being a child with Down syndrome carried a stigma.
"Children were institutionalized by and large. They were separated from societies, from their families," said Dr. Susan Gross, a professor of obstetrics and gynecology at Albert Einstein College of Medicine and Chairperson of OB/GYN at North Bronx Healthcare Network. "There was a time that surgeons would perhaps not operate on a child with Down syndrome."
Walters opened up about her own sister with special needs, who was teased and called "retarded." Palin said some make fun of Trig.
"Some people have been quite cruel," Palin said. "I am on the Internet and ... [have seen] some horrible ads about him that he should have never been born. But, for the most part, people have been so loving and supportive of us that that encourages us and it makes us know that there is ... a lot of hope and there is a lot of love in this country."
Trig accompanied Palin for stints on the campaign trail, which prompted scrutiny. Many said she was exploiting her baby for a political end.
"Wasn't that something? You're kind of, you're damned if you do, damned if you don't," she told Walters. "But I'm very, very proud of my kids, including Trig, and I would do that again in a heartbeat... show the world that I'm proud of this diverse and full and very colorful family that I'm a part of."
Todd Palin joined his wife for portions of the Barbara Walters interview. He brought Trig along too.
Todd said that when his wife shared the news that their son would be born with Down syndrome, he knew his family could handle the challenge.
"I was very excited -- another baby in our family. And when she told me that our child might have Down syndrome, I asked myself, I just, I said, 'Why not us? Our family is never one to have that, you know ...want anybody to feel sorry for us,'' he said. "I knew that our family was strong and would be able to handle whatever was thrown at us."