When Phoebe Harrington and her husband, Benjamin Dumas, welcomed their newborn Benji in 2015, they believed he was born perfectly healthy but soon noticed something was awry.

Fox 5 Atlanta reported that Harrington noticed Benji’s heart was beating rapidly— a maternal instinct that led doctors to further examine Benji and notice a hole between the bottom chambers of his heart. Clinically, Benji had a large ventricular septal defect, Dr. Subhadra Shashidharan, a pediatric cardiothoracic surgeon at Children’s Healthcare of Atlanta, told the news station. Next, Shashidharan and her team performed open heart surgery on Benji, and now, months later, he is better.

"To me, he breathed fast, and that was actually something I noticed right away,” Harrington told Fox 5 Atlanta of the initial warning sign. "I asked all the nurses, ‘Is he breathing fast? Is this normal?’ And they said it was periodic breathing, which is [when] babies breathe fast and then they breathe slow."

After determining his diagnosis upon further examination, doctors wanted to delay Benji’s surgery until he was 6 months old and stronger, but he stopped growing and eating— two signs of heart failure. He also was breathing quickly, with his heart beating over 100 times a minute, Harrington told the news station.

“It was like he was running a marathon,” she told Fox 5 Atlanta.

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In January, at 3 months old weighing only 9 pounds, Benji underwent open heart surgery when his organ was the mere size of a strawberry.

Although the hole in his heart was larger than expected, doctors were able to take a small piece of tissue from the lining of Benji’s heart to patch it.

Today, Benji is healthy and perfect again, his parents told Fox 5 Atlanta.

"It's like he's done a 180,” Harrington told the news station. “And he's just thriving, thriving [as] any baby should."