A baby boy who was born without a large part of his skull is exceeding doctors' expectations at 7 months old.
Lucas Santa Maria was diagnosed with exencephaly in utero. The fatal condition is a rare malformation where brain tissue protrudes and a large part of the skull is missing, according to the U.S. National Library of Medicine's Journal of Pediatric Neurosciences.
Four days after birth, Lucas received surgery to help save his life.
"Even after the surgery they were surprised at how well he was doing," mom Maria Santa Maria of Garfield, New Jersey, told "Good Morning America." "He's eating baby food, getting physical therapy now. He lifts his head up and moves his legs to rock back and forth."
Santa Maria, a mom of four, said she learned her son had exencephaly during the first ultrasound of her pregnancy.
"[A doctor] was showing me on the ultrasound that the skull hadn't closed and the brain was coming outside of the skull," Santa Maria recalled. "All my previous pregnancies I never had anything wrong, so that's something I wasn't expecting."
"The first thing they told me to consider was abortion," she added.
Santa Maria chose to move forward with the pregnancy and welcomed Lucas at Hackensack University Medical Center in Hackensack, New Jersey. Doctors were stunned he survived. But Santa Maria and her husband Augusto made funeral arrangements.
Santa Maria also had a child life specialist prepare her daughters Sophia, 8, Nia, 7 and Giana, 3, in case Lucas didn't make it.
"That broke my heart," Santa Maria said. "I wanted them to meet their baby brother before he had passed and thank God that time never came."
On March 11, Lucas received surgery to close the area around his brain tissue.
Dr. Tim Vogel, chief of pediatric neurosurgery at the North Jersey Brain and Spine Center, said Lucas' surgery entailed removing abnormal brain tissue so it wouldn't damage the functioning area of his brain. The procedure also keeps stroke or seizures from occurring.
(MORE: Mom's Facebook post warns others to not kiss babies after her infant contracts RSV)As Lucas' skull bone grows, Vogel will shave a layer to fill in sunken ares to make sure the brain tissue is protected.
"Lucas is one-of-a-kind in this world," Vogel told "GMA." "He's setting his own records moving forward as a child whose survived these conditions."
"All the medical literature about exencephaly [says] there's never been a person to survive after three hours," Vogel added. "For him to be seven months and meeting milestones...it's a message of hope to other families."
Santa Maria said Lucas child is doing great. He's even cooing and trying to crawl.
"I don't see myself without Lucas," she said. "Sometimes there are miracles. We wanted to meet our baby boy...to us it's a blessing every day."