From the time Shannon Morell underwent in vitro fertilization for the birth of twins in 2006, she and her husband regarded the six leftover frozen embryos as sacred -- unborn children who might one day join their growing family.
The Sterling, Mich., couple had survived the pain of miscarriages, two failed fertility treatments and even a diagnosis of profound deafness in their newborn daughter, but one more cataclysmic event nearly sent their lives spiraling out of control.
On Feb. 17, 2009, they received stunning news from the fertility clinic: All of their frozen embryos had been accidentally transferred into the womb of another woman -- and she was pregnant.
"It was the worst thing my husband and I had to deal with," Shannon Morell told ABCNews.com. "When our daughter Ellie was born profoundly deaf, at least with that we had power. We could take her to the doctor and get a consultant. We knew we could help make her life better with cochlear implants."
"There was a sense of power that we could do something right away," she said. "But in this case we didn't have any control. We felt helpless."
Their next thought was, "Why us?"
Now, in their new book from Simon and Schuster, "Misconception," Shannon and Paul Morell recount their fantastic journey from embryo mix-up to miracle baby.
For 36 weeks, Carolyn Savage of Sylvana, Ohio, carried the couple's child, delivering a healthy 5-pound, 3-ounce boy.
On Sept. 24, 2009, in an act of generosity and faith, Savage, then handed the baby back to his biological parents only 30 minutes after his birth, sealing a connection between the two families that may last a lifetime.
The Savages, who did not respond to requests for an interview, are writing their own book, tentatively titled, "Nine Months to Give," which is due out next year, according to a spokesman for their publisher, HarperOne.
Last year, the Savages went public with their story, saying that because of their Catholic religious beliefs, they did not consider abortion. Those close to the family say that they are struggling with the emotions of their own journey.
The Morells, too, take stock of what they describe as one of the worst years of their life -- full of "constant anxiety and stress" -- as they sat 100 miles away from the Savages, not knowing if the pregnancy would be successful or, as in the case of their daughter, the child might have health issues.
"Nothing could prepare me for the empty feeling I experienced," wrote Shannon Morell, who is now 40. "Worst of all, I could find no books to read for comfort, no similar stories to read for advice and practical tips. Our situation was unique; we were reluctant pioneers in the field of embryonic mishaps."
In vitro fertilization -- the most common type of assisted reproductive technology -- was pioneered in 1978 by doctors in the United Kingdom, and has been used in the United States since 1981.
Of the approximately 62 million women of reproductive age in 2002, about 1.2 million, or 2 percent, had an infertility-related medical appointment within the previous year, and 10 percent had an infertility-related medical visit at some point in their past, according to the Centers for Disease Control.
In 2008, 361 U.S. clinics reported data to the Society for Assisted Reproductive Technology on 140,795 treatment cycles leading to the birth of 56,790 babies.