Some of those defects can be missed.
When Kristi Rosenbaum brought her son Kane home, he was perfectly quiet.
In fact, for 11 days, all he did was sleep.
"I know newborns sleep a lot so I was okay he's just sleepy newborns sleep. but it was all the time. Like we had to wake him up to make him eat," Rosenbaum said.
Kristi and her husband Joshua took Kane to their doctor in Nashville, Ark.
She said he was checked out and sent home.
"After everyone telling you your baby's fine, you can go home, have fun, take care of the baby," Rosenbaum said.
But her instincts told her something was wrong.
"It's just something you feel," It's like a motherly instinct, you know, hey, something's wrong with my baby," Rosenbaum said.
On the eleventh day, she could no longer ignore the uneasy feeling and took Kane to their hospital in Arkandelphia.
Her instincts saved Kane's life.
"It all happened so fast, once we got there he started going downhill so fast," Rosenbaum recalled.
Kane was crashing. His body was shutting down. And his family was in the dark.
"It's weird because you're sitting there and you're praying because you know you're child is in the next room and he's sick," Rosenbaum said. "You see everybody else walking the halls and doing things and living their life but in that moment you're like my life stops."
Kane was air lifted to Arkansas Children's Hospital in Little Rock and diagnosed with hypoplastic left heart syndrome.
"They drew a picture of a normal heart and a picture of his heart with hypoplastic left heart syndrome and there's only half a heart there," Rosenbaum said. "In my mind I'm thinking how is he going to survive with only half a heart."
Three days later, at 14 days old, Kane had his first open heart surgery.
"For the first three or four nights there were a lot of tears shed because we didn't know if he would make it," Rosenbaum said.
But Kane did make it through 60 days in the hospital, two open heart surgeries and a lot of tears.
Now, his story is helping others.
Kristi said Kane's condition should have been discovered earlier, and would have, if he has been screened.
She took his story to the State Capitol, urging lawmakers to pass a bill making pulse oximetry screening mandatory for all newborns.
"I'm proud to say it did pass," Rosenbaum said. "So no baby will go home not screened."
Kane's heart will never be whole.
Kristi lives with the reality that any moment could be his last.
But for now, he's usually a happy baby.
And when he does cry, the tears are a reminder that the baby with half a heart has a whole life ahead of him.