Parents Who Refused to Abort Baby with Brain Outside Skull Open up About Son's Transformative Surgery: 'You Can Feel His Will to Live'

It's been a month since 7-month-old Bentley Yoder underwent surgery to place his brain back into his cranium – and the strong baby who is currently in recovery has a future that is "as bright as his eyes," according to his parents, Sierra and Dustin Yoder.

Bentley was born with a rare congenital disorder called encephalocele, in which a sac-like protrusion of the brain, covered by thin membranes, sits outside the skull. Doctors originally told Sierra and Dustin, who live in Sugarcreek, Ohio, that their son would not survive long after he was born.

"We were unimaginably shocked when we got the dire prognosis," Sierra tells PEOPLE. "The specialist gave us no hope that he would ever live, breathe or thrive. It was gut-wrenching and nerve-wracking to think I was going to have our baby, just to say goodbye as soon as we got to say hello."

She adds, "But he's already proved he's meant for big things. He continues to give the medical field a run for their money."

Sierra and Dustin, both 25, were "heartbroken and confused" when doctors first told them about the condition during an ultrasound to reveal their baby's gender.

"The doctor's face grew pale and I could tell something was wrong," explains Sierra. "They said it was a miracle he survived in-utero for 22 weeks."

They didn't expect their baby to live for more than a few hours after birth – and if he did, doctors predicted he would have little to no brain function.

"If by some chance he did survive, they said he would be a vegetable," says the mother. "A vegetable with no feeling, no pain, no emotions…"

The couple, also parents to 3-year-old Beau, were told to consider abortion as an option after learning of his rare encephalocele condition, which has no known cause and can often lead to death.

"We decided we didn't want him to suffer in a vegetable state so we chose to abort," says Sierra. "The chances of him being okay were the same chances as winning the lottery, is how [doctors] explained it."

But the night before the scheduled abortion, Sierra and Dustin couldn't go through with it.

"My maternal instinct since his diagnosis had been telling me they were wrong about him," says Sierra. "I'm 100 percent glad we [didn't go through with the abortion]. Bentley is an amazing little fighter."

Sierra went into labor around 8 p.m. on October 31, 2015, and Bentley was born nine hours later.

"It was love at first sight. He came out kicking and screaming and breathing – we were so relieved we got even that because it was not what doctors had anticipated," says Sierra.

The parents stayed awake for 36 hours straight after Bentley was born because they were "afraid he was going to take a turn downhill."

"We lived that way until he was 4-weeks-old," says Sierra.

After Bentley was born, Sierra and Dustin went to Boston Children's Hospital, where doctors spent 4 months analyzing Bentley's complex case. The baby's sac-like protrusion stemming from the top of his head appeared to have lots of functional brain tissue inside and his neurosurgeons vowed to save as much as they possibly could.

Surgery was Bentley's only option, as the protrusion grew bigger and was in danger of rupturing.

Boston Children's Hospital neurosurgeon-in-chief Dr. Mark Proctor says his team of almost 40 (including surgeons, anesthesiologists and ICU staffers) practiced on 3-D models for weeks before the operation took place on May 24.

"Many encephalocele cases, you essentially just amputate the part of the brain that's outside [of the head] because it's not functional," Dr. Proctor explains to PEOPLE. "But in his case, we made a great effort to preserve it all."

John Meara, Boston Children’s plastic surgeon-in-chief, says the surgery was extremely successful and he expects the baby's brain to form normally as he grows older. Around 90 percent of the brain tissue in the projection from his cranium was saved.

"We are so positive," Dr. Meara tells PEOPLE. "He bounced back very quickly and he returned back to his baseline, neurologically, very quickly. Several days after [surgery], he was back to where he was beforehand."

He adds, "I have no reason to believe that [his brain] won't grow normally."

Bentley is recovering from his surgery, and although he develops respiratory viruses fairly easily (due to a nasal obstruction), he is recovering on schedule.

"We were terrified of surgery, but we knew it was his only option because otherwise, it was just a ticking time bomb," says Sierra. "People wonder how we could want to put him through so much, and what they don't understand is you can feel his will to live. It's like an aura that surrounds him."

Bentley, a very "curious" and "smiley" baby, according to his mother, continues to thrive and loves spends his time with big brother Beau.

"He truly is a fighter and if there is ever a day when we feel he can't or has no will to continue, then we will accept that," says Sierra. "But that's not the case."