TOLEDO, Ohio -– Carolyn Savage didn't know what to think, what to say, where to look as the ultrasound wand glided over her belly. It was supposed to be her baby inside. Not someone else's.

Yet here she was in her doctor's office with the baby's biological mother, both brought together by a terrible error at a fertility clinic. A doctor, they said, had given Savage the wrong embryo, and now she was carrying the other woman's child.

"The wand is on my abdomen and the technician's talking to someone else: 'There's your baby's nose. There's your baby's head,'" she said. "It was surreal."

Embryo mix-ups at fertility clinics are extremely rare. In those few instances, they've degenerated into custody battles, ugly lawsuits and at least one abortion. But not this time. Savage and her husband decided that the right thing -- the only thing -- to do was to give the baby to the biological parents.

"This was someone else's child," she told The Associated Press on Wednesday. "We didn't know who it was. We didn't know if they didn't have children or if this was their last chance for a child."

"We knew if our child was out there, we'd go to the ends of the earth to get our child back," she said.

Savage, 40, is due to give birth to a boy within the next two weeks via cesarean section. When it happens, biological parents Paul and Shannon Morell, of the Detroit suburb of Troy, Mich., will be nearby, waiting to meet their son.

"How do you thank somebody for what they've done?" Shannon Morell said. "I could say thank you a million different ways."

The Savages say the fertility clinic transferred the wrong frozen embryo to Carolyn's womb in early February. Ten days later, Sean Savage got a call from a doctor saying his wife was pregnant with someone else's child.

"By God's grace, there was never a moment where we thought we were going to have another baby of our own," Carolyn Savage said.

The doctor told them they could abort, but the couple didn't consider that a viable option.

"It wasn't even something we had to discuss," said Sean Savage, 39.

The Savages won't reveal the name of the fertility clinic, saying only that it's not in Ohio. They have hired attorneys who say they are working to make sure the clinic will accept full responsibility.

A message was left Wednesday for the Savages' Detroit attorney, Brian McKeen.

The Morells, who live north of Detroit, learned of the mistake a day after the Savages. They were just about to start the process of having another baby with their last embryos when the clinic called.

The two couples knew nothing about each other. Shannon Morell feared that the pregnant woman would choose abortion, ending their chance to give their 2-year-old twin girls a sibling.

"I didn't think she'd want to carry the baby to term," Shannon said. "I felt helpless."

A few days passed before they learned that the Savages were not only willing to continue with the pregnancy, but also to hand over the baby without hesitation.

In the first few weeks, the Savages sent e-mail updates after every doctor's visit. The couples finally met about three months into the pregnancy.