A baby born with a cleft palate can smile properly for the first time after undergoing life-changing surgery to rebuild his mouth.

Little 6-month-old Cam Martin looks unrecognizable after a plastic surgeon spent five hours fixing his top lip and gum.

Cam was born two minutes after his twin brother Jack on April 3 to parents Matt and Sara Martin.

But unlike his sibling, Cam had a cleft palate, meaning his upper lip, the bones of his upper jaw and his gum were split.

The defect meant Cam was unable to breastfeed and had to be fed through a bottle with a special valve.

Dad Matt, 29, and his wife Sara, 27, met with plastic surgeons who advised that Cam would need a series of operations to rebuild his mouth.

On July 25, he underwent the grueling operation to repair his upper lip - and the results are incredible.

Adorable photos show the youngster beaming widely a few days after the surgery at Medical City Dallas Hospital.

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"It was a full face smile. He was giving the biggest grin he could," Matt, a filmmaker from Forney, said. "Sara and I cried because we were beginning to think we’d never see him smile. The beam was in his eyes and in his cheeks. He was saying: ‘I’m still here, I’m still the same baby, everything’s OK.'”

Cam’s cleft lip and palate were not picked up in any of Sara’s sonograms before the birth.

But Matt said that as soon as he was born at Texas Health Presbyterian Hospital, he and Sara, a dental assistant, knew something was wrong.

“No one said anything at first. I went over to see Cam and the nurses were all huddled together," he said. “I had never seen anything like his face before. I had no idea what I was looking at. A nurse told me he had a cleft lip and palate and that they needed to work out how he was going to eat and breathe.”

Cam's cleft lip and palate were not detected in mom Sara's sonograms.

Cam's cleft lip and palate were not detected in mom Sara's sonograms. (SWNS)

After a few days on the neonatal intensive care unit, Cam returned home with his parents.

In the weeks that followed, the couple visited a plastic surgeon who explained that Cam would require three operations to rebuild his mouth.

The first operation would rebuild Cam’s upper lip. The second, when he was 18 months, would repair the roof of his mouth.

The final procedure would be a bone graft to rebuild his gum when he was between 4 and 7.

Baby Cam was fitted with a mouthpiece, known as a NAM device, which covered the roof of his mouth to stretch out the area in preparation for the first operation.

“The mouthpiece had little balls that were fitted into Cam’s nostrils to stretch out the skin between his nose and mouth," he said. “We had to go in every week for them to adjust it. We hated seeing Cam in pain and we did wonder whether we were doing the right thing.”

When Cam was just 3 months old, he went through the operation to fix his upper lip.

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“Doctors stitched his lip together where it was split so that his lip was no longer in three parts," Matt said. “It was really hard to hand him over for surgery. When the nurses gave him back he was screaming. They had him on morphine and his face was swollen and bruised and bloody. It was like we had been given back a different baby."

“He cried the whole day. We had to feed him with a syringe after the operation," he said. “I hated knowing that something we had chosen, the operation, had caused so much pain for our son.”

Cam, pictured with his twin brother, faces two more surgeries in his future.

Cam, pictured with his twin brother, faces two more surgeries in his future. (SWNS)

But a few days after the operation, as the swelling went down and the bruising healed, Matt and Sara were rewarded by seeing Cam smile for the first time with his full upper lip.

“Sara was changing his diaper and I was watching TV," Matt said. "She started screaming, ‘Come in here, he’s smiling!’ I rushed in. I couldn’t believe it. In my darkest moments, I thought I’d never see him smile with a healed top lip but here he was beaming at me.”

Matt wanted to give hope to other parents who are struggling with a baby with a cleft palate.

“It is terrifying but the scariest part is before you go and talk to surgeons," he said. “Once you get your doctor and a solid team in place, it gets a lot less scary. You fall in love with your baby and it doesn’t matter whether they have a cleft palate or not.”