WASHINGTON • One night last year, paediatric doctor Victoria Rodriguez, who works in a hospital in Chicago, was paged from the emergency room for a consultation.

A doctor had evaluated a four-week-old infant. He could not find anything wrong, but hesitated to send the anxious family home.

During the night, the parents had received an alarm on their phones that the baby's heart rate and blood-oxygen level were low.

The alarm had been triggered by the baby's high-tech sock, one of a new class of devices that continuously measure vital signs. There is no peer-reviewed research on the accuracy of these devices. They have not been evaluated by the Food and Drug Administration.

These new monitors come in several forms, with wireless electronics integrated into socks, leg bands, buttons or diaper clips that send data to parents' smartphones.

Some use motion sensors that purport to detect when a baby stops breathing.

Others use pulse-oximetry probes, which shine a light through the skin to measure blood-oxygen levels. The devices can be purchased online and at major retailers for US$90 (S$ 127) to US$350.

They track vital signs, but it is not clear how accurate this information is or how it should be used by parents and medical providers.

In the case Dr Rodriguez was consulted on, she felt that she had to recommend that the baby be hospitalised for more testing.

After 24 hours of monitoring - no problems cropped up - the infant was cleared to go home.

Dr Eric Coon, an assistant professor of paediatrics at the University of Utah School of Medicine, has overseen the care of three infants with similar stories.

In each case, the hospital stays were "of questionable value". "Hospitalisation carries a whole host of potential harm," he warned, including hospital-acquired infections.

Parents might assume that a monitor that measures vital signs could prevent their baby from dying of sudden infant death syndrome (Sids), but there is no hard evidence. And studies from the 1980s and 1990s of hospital-grade heart-rate and breathing monitors prescribed for home use for babies thought to be at high risk of Sids found that the monitors did not reduce the risk.

These older monitors were more cumbersome, but some studies reported that their use increased parental stress and fatigue.

In its guidelines on Sids prevention, the American Academy of Paediatrics says: "Do not use home cardio-respiratory monitors as a strategy to reduce the risk."

Manufacturers do not claim that new monitors prevent Sids or other sleep-related deaths, only that they offer "peace of mind". As the devices do not claim to be medical equipment, they do not fall under the regulation of the US Food and Drug Administration.

Paediatrician Christopher Bonafide, who works at the Children's Hospital of Philadelphia, emphasises proven strategies.

"There are things that we know help in terms of prevention of Sids, such as a bare crib and flat mattress with a tight crib sheet. These are not smartphone-integrated things but they are effective," he said.

WASHINGTON POST