The day Brandon Diallo was born, no one had an inkling there was anything wrong with him.

But in the middle of his second night at Virtua Memorial in Mount Holly, a nurse fastened a small oxygen sensor to his hand and foot.

And then things started to happen in a hurry.

After a helicopter flight in the early hours of Nov. 13 and delicate heart surgery at Children's Hospital of Philadelphia, the brown-eyed baby is just fine. But if not for the initial test at Virtua, required by a state law that took effect Aug. 31, doctors say brain damage was likely.

New Jersey officials say Brandon is at least the second baby whose critical heart defect was detected by the test, an infant-size version of the pulse oximetry screening commonly done on adult patients. The other "save" took place in September, at Newton Medical Center in Sussex County.

New Jersey's is the first such law in the country. A few states have followed suit, while other such measures are under consideration, including in Pennsylvania. U.S. Secretary of Health and Human Services Kathleen Sebelius has recommended that all newborns receive "pulse ox," which costs just a few dollars and takes minutes.

Mamadou and Lorretta Diallo, Brandon's parents, were by his side in the middle of the night when a nurse came to get the baby for the test.

When he didn't return soon, Lorretta Diallo started to worry and asked her husband to go check. "I didn't know what was going on," she said.

Nurses were so surprised by Brandon's oxygen level - it was 40 percent saturation, whereas normal readings are in the 90s - that they did the test again. The result was the same, and he was immediately intubated and soon on the helicopter to Children's Hospital. An echocardiogram revealed that the two large arteries carrying blood from his heart were transposed.

As a result, the "blue" blood that was sent to his heart from various parts of the body for oxygenation was not sent on to the lungs. Instead, it was simply returned straight back to the body, said Aaron Dorfman, a pediatric cardiologist at Children's Specialty Care Center in Voorhees, where Brandon has been for a checkup.

The little blood that was oxygenated by his lungs, meanwhile, was sent back to the lungs, over and over in a grim cycle. This defect occurs a few dozen times per 100,000 live births, Dorfman said.

It is perhaps the hardest type of heart defect to detect with prenatal testing. It also is not readily apparent to the eye after birth, especially in a dark-skinned baby, like Brandon, who did not appear "blue," Dorfman said.

Depending on the defect's severity, such babies can manage for a few days, even weeks.

Newborns have a hole in their heart that allows them to receive oxygenated blood from the mother during pregnancy - a hole that closes within a day or two, said Denise Bell, chief of pediatrics at Virtua Memorial.

Some babies have an additional hole that allows continued mixing of the oxygenated and unoxygenated blood.

But Brandon did not. At Children's, he was taken from the helipad straight to the cardiac-catheterization lab, where clinicians performed a balloon atrial septostomy - a stabilization procedure pioneered at the hospital in the 1960s, which opens a temporary hole in the heart.

A few days later, surgeon Stephanie Fuller gingerly detached the transposed arteries and reconnected them in their proper places - a procedure that was not perfected until the 1980s.

It was all news to the Diallos, who live in Burlington Township and are both sergeants in the Army - he at Joint Base McGuire-Dix-Lakehurst, she in Trenton.

Mamadou Diallo said he had been unaware of the requirement for pulse oximetry on newborns, not to mention the heart defect itself. "I'm very thankful that they do have that requirement," he said.

Dorfman said that some babies who undergo major heart surgery such as this one may experience subtle cognitive or behavioral issues later in life. But years ago, they were likely to die.

Now, Dorfman said, "they do great."

Some health officials have warned that the use of pulse ox on infants would lead to expensive follow-up tests that, in most cases, would prove unnecessary. Dorfman said this has not been a problem thus far in New Jersey.

The law was predicted to catch dozens of critical heart defects each year in New Jersey that would otherwise have been missed.

So, while Dorfman is not surprised to see a case like Brandon's, he said it was exciting.

"Babies," the cardiologist said, "are really being saved by this."