TORONTO - Watching Kristine Barry and husband Christopher Havill cuddle their two-month-old son Sebastian, it's hard to believe their little guy has been through more major medical procedures in his short life - and even before being born - than many people experience in a lifetime.

Weeks before his birth in May, Toronto doctors discovered through imaging scans that Sebastian had not one, but two congenital heart defects - and they knew they had to do something fairly radical to bring him into the world and give him a chance at a full and healthy life.

That something was an in-utero procedure to poke a hole in the wall between the upper chambers of his tiny heart, which had developed with no opening, followed by an operation after birth to repair his major cardiac arteries, which weren't in the proper locations.

Scans of Sebastian while in his mother's womb showed his aorta, the vessel that takes oxygen-rich blood to the brain and body, and his pulmonary artery, which channels blood to the lungs to be oxygenated, were switched - a condition known as transposition of the great arteries, or TGA.

Doctors also discovered there were no openings in the walls between either the two upper chambers (the atria) of his heart or the bottom two chambers (the ventricles), which would have prevented his blood from circulating properly after birth. While in the womb, fetal blood is oxygenated through the placenta.

“If a baby doesn't have any holes between the two sides, so the right and left half, the child would be deeply blue, and eventually will die from this condition unless we are able to create the hole after birth rapidly,” said cardiologist Dr. Edgar Jaeggi, head of the fetal cardiac program at Sick Kids Hospital and part of the two-hospital team that cared for Barry and her soon-to-be born baby.

“This is a life-threatening condition that could result in rapid brain damage, with the baby doing very poorly and dying from this,” Jaeggi explained.

However, after Sebastian's birth, doctors would have had only a few minutes to open up his chest and repair his heart, requiring full neonatal resuscitation and cardiac surgery teams to be on stand-by.

To avoid such a high-risk delivery and the dangers to the newborn, a team of doctors from Mount Sinai Hospital and Sick Kids opted to perform the procedure to create an opening between the upper chambers of Sebastian's heart while he was in the womb.

“It's pretty intense hearing something like that, that they're going to do it while he's still inside of her,” Havill, 27, said Tuesday after he and his wife travelled to Sick Kids from their home in Barrie, Ont., north of Toronto.

“It's something you would think would only happen on a TV medical show, not in real life,” agreed Barry, 25. “Doing the in-utero procedure actually sounded like the best possible thing. In my gut, we knew this was what we wanted to happen, what we needed to do.”

On May 18, doctors at Mount Sinai took the first steps, injecting drugs through Barry's abdomen that put Sebastian to sleep, paralyzed his body to prevent him from moving, and provided pain relief.

“The baby obviously has to be in the right position,” said Dr. Greg Ryan, head of the fetal medicine program at Mount Sinai.

“Because if the baby is not aligned in-utero, it's a non-starter, and we've sometimes had to wait for two or three days for the baby to come into position where it gives us our best shot - because you have one shot and you need to make that work.”

Barry was then transported to Sick Kids across the street via an underground tunnel that connects the two hospitals, where Ryan performed the next part of the procedure under ultrasound-guided imagery, inserting a fine needle through Barry's abdomen and uterus, then into the upper chamber of Sebastian's heart and passing it through the wall to the adjacent atrium.

A catheter was then fed through the needle and a tiny balloon inserted between the wall, a process that's similar to balloon angioplasty to open up a blocked coronary artery in those at risk of a heart attack.

“Then, essentially, we blow up the balloon in that wall which had been closed,” explained Ryan. “By blowing it up, we could open up a hole in the wall between the two chambers, and this allows the mixing of the blood.

“Once we've done that, we withdraw the needle and withdraw the catheter out of the baby's heart,” he said, adding that he believes this is the first time in the world that the in-utero procedure has been performed in a fetus with TGA.

Jaeggi said the team waited until Sebastian was almost full-term to do the in-utero surgery - called a balloon atrial septoplasty, or BAS - because doing so earlier might have allowed the hole to close up again.

“We wanted the biggest hole closest to delivery,” he said, describing the opening as about 3.5 millimetres in diameter.

On May 23, Barry gave birth through a regular vaginal delivery after being induced and Sebastian was born “pink and screaming.”

“They always primed us that we would be having a blue baby, so when he came out, I'm like 'That's not blue,”' said Barry, recalling her huge sense of relief. “He was here and he looked as babies should when they're born.”

Sebastian had a second BAS procedure after birth to ensure the atrial opening was large enough. Then five days later, surgeons at Sick Kids performed open-heart surgery on the infant to switch his aorta and pulmonary artery into their proper positions.

Now weighing 10 pounds and meeting all his developmental milestones, Sebastian is like any other healthy two-month-old, his parents say.

“He's a pretty calm, pretty chill baby. He lets us know when he's not happy. He still has that very strong set of lungs that he was born with,” Barry said. “We just recently started getting our smiles from him.”

“You barely even know that anything had happened to him unless you take off his shirt and see his scars,” added Havill. “He's just awesome.”

The couple say it's hard to express how grateful they are to the medical teams at the two hospitals.

“Thank you doesn't seem like enough, but definitely thanks to them for saving my baby's life,” Barry said.

“It's just amazing what they're able and capable of doing.”