Lisa Rodebaugh took her 4-day-old baby boy to the emergency room because he had stopped eating and kept screaming. Once there, he suffered cardiac arrest and a stroke, and was soon on his way to Children's Hospital of Philadelphia for the first of three heart surgeries.

Score one for a mother's intuition. But if nurses had performed a cheap, simple test three days earlier - before Andrew went home from the hospital the first time - his heart defect might have been caught before the stroke.

Cases such as this one are fueling a growing movement to require that all newborns get the test, called pulse oximetry, which measures oxygen levels in the blood.

On Aug. 31, New Jersey became the first state to require the test, a modified version of what is familiar to many adult patients as "pulse ox." A similar measure has been introduced in Pennsylvania, and some hospitals, including those in the Main Line Health group, already have chosen to do the test without being required.

Last week, Secretary of Health and Human Services Kathleen Sebelius added pulse ox to the list of nearly 60 recommended tests for newborns - a list that states are not bound to follow, though many do, in large part.

By measuring a baby's oxygen level, hospitals are better able to detect any of a group of half a dozen critical heart defects, which occur in two to three births per 1,000.

These defects also can be detected by fetal ultrasound or a physical exam after birth, but these tests miss about one out of the two to three defects per 1,000, said pediatric cardiologist Terry Anderson of Children's Hospital of Philadelphia's specialty care center in Voorhees.

Sometimes a newborn with a severe problem simply will appear normal for several days, as happened 10 years ago with Rodebaugh's son, who had a condition called hypoplastic left heart syndrome. By evening of his third day, he started to go downhill.

"He wouldn't eat, he wouldn't do anything," his mother recalled. "He was just struggling."

Andrew's surgeries were successful, but he has some developmental issues, including speech that is a little unclear, she said, attributing it to the stroke.

Pulse oximetry does not guarantee all defects will be diagnosed, Anderson said. By itself, the test is about 60 to 70 percent sensitive. But when it is combined with ultrasound and a physical exam, clinicians are able to detect more than 90 percent of cases, he said.

Anderson, who was part of a working group that established protocols for New Jersey's program, estimated it would catch perhaps 100 cases a year that otherwise would have been missed.

A spokeswoman for at least one hospital - Hackensack University Medical Center - said pulse oximetry led to a heart-defect diagnosis that might have gone undetected.

The prime sponsor of the Assembly version of the New Jersey bill was Assemblyman Jason O'Donnell (D., Hudson), whose son had a heart defect that was caught through a physical exam.

In both adults and infants, oxygen levels are determined by shining red and infrared light through the skin and measuring how much of each is absorbed. Adults are tested with a device that fits over the fingertip; newborns are tested with a smaller, flexible strip that wraps around the hand or foot like a bandage.

The test takes just a couple of minutes, as demonstrated last week by Lara Mitchell, a nurse educator and clinical advanced practice nurse at Virtua Voorhees.

She tested newborn Semya Denise Marshall, taking readings from both her hand (97 percent oxygen saturation) and foot (98 percent).

Had either one been below 90 percent, Semya would have failed the test, and a cardiologist would have been summoned. Had either reading been below 95 percent, or if the two numbers had been more than 3 points apart, indicating a possible abnormality, she would have been retested in an hour.

The baby's mother, Rachel Lorenzo of Berlin, had not heard of the testing requirement, but was intrigued.

"It's good to be proactive," Lorenzo said.

So far, Virtua Voorhees has not detected any heart defects among several hundred babies screened since the law took effect, said Mitchell, the nurse educator.

Initially, some professional groups were hesitant about endorsing the test for all babies, arguing that different standards would be needed in the thinner air of high altitudes and that special arrangements might be needed in rural hospitals that don't have immediate access to a pediatric cardiologist.

"They have to work out what we do for babies born in Denver," said Gerard R. Martin, pediatric cardiologist at Children's National Medical Center in Washington. In rural hospitals, he said, doctors might get an off-site cardiologist to read test results via the Internet.

On the plus side, pulse oximetry costs just a few dollars, the amount varying based on whether a reusable strip is employed.

Main Line Health's hospitals started doing the test on newborns in early 2010, said Robert Stavis, chairman of pediatrics at Bryn Mawr, Lankenau, and Paoli Hospitals.

"It just didn't seem like there was a downside to it," Stavis said.

Rodebaugh, the woman whose son had hypoplastic left heart syndrome, is convinced that if his oxygen levels had been measured when he was born at Abington Memorial Hospital, he would never have had the stroke.

Steven Shapiro, Abington's chairman of pediatrics, said he could not comment on the case without authorization and without knowing the details. He said Abington will not conduct pulse oximetry on newborns without further consideration, cautioning that there would be some false positives and some cases in which echocardiograms were done unnecessarily.

"It's good science," he said of the studies that show a benefit to such testing. "You've got to be very careful."

The rate of false positives has gone down in recent years, with better devices that are not thrown off by the baby's motion. A recent study found a false positive rate of about three cases per 10,000.

At Main Line Health, the false positive rate has been even lower. Those hospitals haven't caught any real cases either, Stavis said. But they're going to keep doing the test just in case.