Lori Berenson was plagued with medical problems, many of which developed in her first two years at a frigid maximum security prison with no heat and running water at 12,800 feet above sea level near the Bolivian border.
"I've seen her age," Berenson, a statistics professor at Montclair State University in New Jersey, told ABCNew.com last year. "It was a miracle she could become pregnant."
In 2009, his daughter underwent seven hours of surgery to repair a slipped disk in her vertebrae.
Berenson's story began in 1995, when she was arrested at the age of 26 on suspicion of aiding leftist rebels.
She was sentenced at first to life imprisonment, but a civilian court retried her in 2000 and convicted her of a lesser crime of terrorist collaboration and reduced her sentence. All along, she has denied any wrongdoing.
In prison, she met Apari, now a lawyer and former member of the Tupac Amaru Revolutionary Movement, which was best known for its four-month takeover of the Japanese ambassador's residence in 1996 in Lima.
Berenson married Apari in 2003 when he was released from prison, and gave birth to Salvador in November and is raising him as a "single mom," according to her father.
According to the Berensons, their daughter will be expelled from Peru. Her son has dual U.S.-Peruvian citizenship and his grandparents said they have considered taking custody of the child.
Rhoda and Mark Berenson have made numerous trips to Peru -- about six a year over the last 15 years -- to visit their daughter in a variety of prisons. They were with her in Lima for the birth of their grandson in 2009 and again before Thanksgiving for her spinal surgery.
"It was really horrible in the beginning, but it has improved for Lori and all the prisoners," said Rhoda Berenson.
The concrete prison from where she will be released in the next 24 hours has few amenities. Water comes only once a day and prisoners store it for personal use. There are no regular toilets.
"She does a lot of squatting and is exposed to the elements, but it's not that cold," said her mother last year.
Rhoda Berenson said the birth of Salvador had a "huge effect on her in a very positive way."
"In those horrible years, something really wonderful came of it," she said. "Giving birth to Salvador meant that in spite of the Peruvian government's attempts to ruin her life, they didn't deprive her of motherhood."
Lori Berenson has said she still wants to help others and even though it's too late for her to become a doctor. Her mother said she told her she would like to do something "medically related" when she gets out of prison.
"She is still more interested in helping people than becoming rich," Rhoda Berenson said. "Those things haven't changed.
"Although the prison conditions are certainly stark -- particularly during the early years in the Andes when it was bitter cold -- and I had many concerns about Lori's health over the years, I always knew Lori was strong and would endure," she said.
"If someone told me years ago that this would happen, I would say I am just going to go in a cave and disappear," she said. "But you manage it. You have to prepare yourself somehow by trying to even out the ups and downs."