Within four days of finding out she was pregnant, Carolyn Savage went from the high of anticipating the child she had tried so hard to conceive to the unfathomable low of knowing the baby was not hers to keep.
Carolyn Savage had had a history of miscarriages, and she and her husband, Sean Savage, turned to in vitro fertilization, hoping to have a fourth child.
But On Feb. 16, 2009, the Sylvana, Ohio, couple learned that the frozen embryo of another couple had been mistakenly transferred into Carolyn's womb.
The Savages could have fought for custody, or Carolyn could have had an abortion. Tethered to a strong Catholic faith, Carolyn chose to carry the baby she and Sean called "Little Man" to term.
On Sept. 24, 2009, the Savages returned their newborn son, whom they'd held for 30 minutes, to his biological parents -- Shannon and Paul Morell of Sterling Heights, Mich., who named him Logan.
In the 17 months since Logan's birth, the Savages have had a long, painful, somewhat "ambiguous" journey, which they've described in their new book, "Inconceivable."
"We have three children. Or do we have four? A strange question, but the kind that parents who have lost a child ask themselves from time to time. That absent child is always with you, a loss you feel some days as yearning and other days in a gasp of pain.
"This was a child whom I nurtured and we both protected from the forces conspiring against his survival," writes Carolyn, now 41, in the book's prologue. "Yet I understand that I may never hold him in my arms again and that the next time I see him, he will think of me as a stranger."
Throughout the 36 weeks that Carolyn carried "Little Man," the two couples maintained a respectful relationship. The Morells described in their 2010 book, "Misconception," their own harrowing wait, knowing that with Carolyn's past history of miscarriages, their child might never be born.
In an interview with ABCNews.com, the Savages revealed that even though they considered it a "gift" to return Logan to his biological parents, the horrific mistake tore apart their lives.
Their marriage was under tremendous strain, and after the delivery, Carolyn was diagnosed with post-traumatic stress disorder. Both continue to seek counseling.
Part of the problem was their loss was "ambiguous": Their son had not died, but he was gone.
"It's a loss that has no closure," said by Pauline Boss, professor emeritus at the University of Minnesota, who described the ambiguity in her book, "Ambiguous Loss."
"People have a difficult time resolving this," she told ABCNews.com. "There are no rituals or sympathy cards for them."
"He'll always be my baby, even though he's their son," said Carolyn. "There was no way of entering into a pregnancy and taking a 12-cell embryo and turning it into a human being and not feel a maternal connection to him."
The embryo mix-up happened at a fertility clinic that a legal settlement prohibits the Savages from naming, but the May 2010 agreement required them to explain in writing what went wrong.
A lab employee where the frozen embryos were stored had labeled Carolyn's birth year as 3/19/1967, rather than 3/19/1969 -- a detail that helped identify the eventual error.
Embryos are stored alphabetically, and when the clinic opened the "S" file, it mistakenly pulled an information sheet for Shannon Savage, who used her birth name at the time of the original IVF procedure.