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.
Embryo mix-ups, where fertilized eggs have been placed in the wrong womb, have only been reported a handful of times worldwide, and in all cases they were devastating to all parties and landed in the courts.
Both the Morells and the Savages hired attorneys, but were hailed for their civility in determining parental rights.
"I have never seen a case like this before," said Ellen Essig, the Cincinnati lawyer who represented the Morells in securing legal parentage.
Law varies from state to state, but in Ohio, it is presumed that the person giving birth to the child is the mother and that if she is married, her husband is the father.
Early on, the couples determined that the mix-up had occurred because they shared a common name. Shannon had enrolled at the clinic under her maiden name, Savage. Honoring that connection, they eventually named their now active 7-month-old son Logan Savage Morell.
Shannon and Paul Morell had spent four years trying to conceive through IVF. She had suffered two miscarriages and after three attempts got pregnant with twins, now nearly three years old. As Ellie underwent surgery for cochlear implants, the couple put off trying for a third child. But they had always planned to use the remaining six embryos.
Carolyn and Sean Savage, who have three sons, aged 15 to 2, had also turned to IVF to conceive their youngest child after numerous miscarriages. The couple returned the same clinic last year to try for more children.
But along with news of her fourth pregnancy came the almost unbelievable phone call from their doctor that the growing fetus belonged to the Morells.
At first the Morells worried that the Savages, whose name they didn't learn for months, would decide to abort. Then, knowing Carolyn had also had fertility issues, they were anxious about miscarriage. Given their daughter's deafness in both ears, they thought there might be health issues.
Would she deliver, one, two or three babies? "We looked at our little house and wondered, 'What if we had three?'," said Morell. "Then we realized our first concern was that she continue the pregnancy. Nothing else mattered."
Only getting brief updates through lawyers, the Morells were too afraid to tell family and friends about the "secret baby" they affectionately called "peanut."
Shannon Morell, an eighth-grade teacher, eventually confided with mixed emotion in a colleague who was pregnant.
"She would be like a mirror," wrote Morell. "I'd be able to imagine what the other woman looked like, as if she carried our child."
Morell offered the friend baby clothes, then her heart swelled with regret. "The realization that I never be pregnant again was so final, almost as if I had agreed to have a hysterectomy or had unexpectedly found myself in the midst of menopause."
"We'd been cheated," she wrote. "Though Paul and I were expecting a child, we were missing out on the entire experience. We would never feel our child move beneath my skin or see his little hands flutter beneath my belly and explain that Mama was carrying their little brother or sister inside of her. It wasn't right. It wasn't fair. I should be wearing those maternity clothes."
After 14 weeks, when the pregnancy was viable, the Morells received a call that the Savages wanted to meet. The encounter was "tense and awkward," with Shannon spilling out her heart but Carolyn keeping her emotional distance. Still, both parties wanted to "make a connection."
"I don't know who I felt sorrier for in the room," said the Morell's lawyer, Essig. "It was a gathering of four very sad people for reasons none of them had any control over. Until then, I had never been in a meeting like that. I deal with a lot of things, but this was heart-wrenching and they were all so generous in their approach."
Morell tried to put herself in Savage's shoes. "Our roles could have been reversed," she said. "What would I do? She didn't ask for this. She didn't try to hurt me."
The relationship warmed as the two women began to e-mail each other and Carolyn Savage sent photos from the doctor's visits. Eventually, Shannon Morell was invited to an ultrasound appointment.
Savage went into labor one month early and delivered by Caesarian section as the Morells waited in a separate room near the neonatal unit. Shannon said she fought back tears and felt joy tinged with "regret, pain and even a touch of jealousy."
"That's when it really hit me: I'm not there," she wrote. "I will never hear Logan's first cries, I will never be the first one to see him, I will never behold him all goopy from birth or see him open his eyes for the first time."
A half-hour after Logan's birth, Sean Savage brought the baby to the Morells.
"The repressed emotions of an entire pregnancy exploded in the first few minutes of meeting my son," she wrote. "I'm not a huggy person, but I threw my arms around Sean and thanked him."
The next day, the families met again with their siblings. Not once did the Morells doubt that the Savages would keep their word.
"They are ethical people and throughout the whole time, they were never wishy-washy," said Morell. "She knew, right away from the first month, that the baby wasn't hers."
The day the couples parted, the Savages presented the Morells with a "treasure chest," filled with baby Nikes, a preemie outfit, hats, children's books and a framed photo of Logan emerging into the world.
The families have maintained frequent contact in the months since Logan's birth through e-mails, telephone calls and letters.
"We went to see them over the holidays when [Logan] was three months old and met their kids," said Shannon Morell. "We had a good time. The stress of the whole situation was over and my daughters loved their little girl. I can say we are friends."
The Savages don't expect constant contact with Logan, but Morell hopes that one day when he learns the story of his conception, he will already be comfortable with his other family.
Knowing that the Savages still had eight frozen embryos to try another pregnancy, Morell impulsively offered to undergo IVF so they might have their fourth child.
"Carolyn is going to try to get pregnant again," said Morell. "But they are looking for a surrogate who doesn't bond with the baby."
The Morells reached an "agreement" with the unnamed fertility clinic. "They took responsibility over our contract and we are satisfied," she said.
The Savages have retained a New York City attorney, according Howard J. Rubenstein, the agency that represented them at the time of the birth, but the couple has not said publicly if they will pursue legal action.
By writing the book, the Morells advise prospective parents to better research fertility clinics, particularly their protocols for handling embryos. "You are dealing with human life," she said. "People need to be proactive."
Shannon Morell is still trying to figure out God's plan for her agonizing efforts to raise a family -- perhaps that Logan might one day bring "great good" to the world.
"I don't think I will know for awhile," she said. "I think everything happens for a reason. Just when you think you are going through personal growth and learn lessons why, there are more tough times. I try to take what life gives you and make the best of it."
"If I hadn't found out [about the embryo mix-up], I would have been OK with it," said Morell. "My kid would have had a great life, raised by a large family, educated in a Christian household that values education. He would have been fine."
From the start, Morell has called Carolyn Savage her "guardian angel," and her book acknowledges her monumental sacrifice: "Thank you for nurturing our son, protecting him and most of all, loving him enough to let him go."