Keri and Chad McCartney were looking forward to learning whether the baby Keri was carrying was a boy or a girl. But the moment an image swam onto the screen at a Texas doctor's office last Feb. 15, the technician fell silent. When Keri, 40, and Chad, 39, a pastor, peered closer, they saw a bulge below the fetus. "What's that?" they asked. "Well, it's a mass," came the answer. Then Dr. Debra Williams delivered difficult news: The tailbone attachment was a rare tumor, present in 1 of 35,000 pregnancies, that draws on the fetal blood supply. The baby's odds of survival? Less than 10 percent.

Within days the fetus was close to heart failure. "I felt like I was in no man's land," says Keri. Their best hope was a surgery that would remove the tumor, then return the baby to the uterus. But few such operations had ever been performed—and not all of them successfully. On Feb. 28, during a four-hour procedure at Texas Children's Hospital in Houston, surgeons opened Keri's womb, partially removed the 25-week-old fetus and cut away most of the tumor. Then, says Dr. Kenneth Moise, "we put everything back the way we found it." Ten weeks later Macie made her second appearance, this time via C-section. A robust 6 lbs. 1 oz., she had surgery at 9 days to remove the rest of the tumor. Her prognosis: strong. She went home last week. Says her giddy mom: "She's like, 'I fought, I'm here, I'm done. Now, I can relax.'"

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