ANN ARBOR, Mich. -

Seven month-old Bella Bibler is all smiles.

There's no hint of the open heart surgery she had just two months ago.

"She actually recovered faster than they expected. She was only in the hospital for five days," said Bella's mother Joni Bibler.

Bella was born last August 16th at a hospital in Jackson, Michigan. She seemed perfectly healthy.

"It was 10 o'clock the day after she was born, and they took her for her routine screening," said Bibler.

When they were gone for nearly an hour, Bella's parents became nervous.

"Next thing I know, in comes my nurses and the pediatrician, and then they told us that her oxygen levels were really low, they had her on two oxygen machines, and they were calling U of M to come get her," said Joni Bibler.

It was a simple test called a pulse oximetry, or "pulse ox" for short, that detected Bella's serious heart issue -- a combination of four heart defects called tetralogy of Fallot.

"Babies normally should have an oxygen level between 95 and 99 percent," said Dr. Ronald Grifka, a pediatric cardiologist at the University of Michigan's C.S. Mott Children's Hospital. "If the oxygen level is less than that, it may indicate that there is a heart problem."

Grifka and others worked with the state to make the test mandatory for newborns in Michigan.

"There's no needle pokes, no blood draws, just a little probe that is really like a Band-Aid that has a sensor," said Grifka. "In the state of Michigan, we estimate every year with this screening test, checking the oxygen level, we're going to pick up about 80 to 100 babies every year. Some of these babies could have gone home and gotten really critically ill before the parents could have noticed a problem and brought them for medical care."

Grifka said one out of every 100 babies will be born with a heart defect and up to half of those problems are not detected before the baby is born.

Joni Bibler had several ultrasounds during her pregnancy, and none of them showed an issue with Bella's heart. Doctors say that's why the pulse oximetry test is so critical.

Bella is doing great and already trying to crawl and stand on her own. Her parents are grateful she got the test.

"It's very scary to think what could have happened if we just would have been told we could home," said Bella's father Joseph Bibler. "Glad they did it and glad it's going to continue to be done from this point on, so hopefully they can catch other kids that have it."