DALLAS (CBSDFW.COM) – No one was sure how long Griffin Moore would survive.  Born premature, weighing just 3 pounds, he had a life-threatening heart defect.  “He was the sickest baby in the NICU here at Medical City,” said his mother, Ashley Moore.

His family turned to Medical City Children’s Hospital in Dallas, hoping doctors could help him survive.  “He had essentially no way for his blood to get from his heart to his lungs to get oxygen,” explains Dr. Grant Burton.

Griffin didn’t come alone.  Lying side by side, he and his twin sister, Georgia, were suffering from the same condition, although varying in degree.  “Georgia had a small pulmonary artery… Griffin, on the other hand, had really no pulmonary artery.  His was so small it was essentially gone,” said. Dr. Burton.

Operating on tiny babies requires tiny, even microscopic tools, and doctors say the surgery Griffin needed would be a technically difficult feat.  “Honestly, you know, fifty years ago, nobody would have thought about a surgery like this. It’s almost universally fatal,” said Dr. Burton.

Griffin had to gain a little weight first. When he made it to four pounds, though, doctors took him to the operating table.  Now at two-and-a-half months old, he is recovering.  “He’s doing really well. Huge difference,” said Moore.

In fact, he’s getting ready to go home for the very first time. His sister, Georgia, is expected to join him next week and eventually undergo her own surgery.