Scientists in Australia have found that some babies at risk of sudden infant death syndrome, or SIDS, have low levels of an enzyme called butyrylcholinesterase (BChE) in their blood.

And while public health campaigns have drastically reduced the incidence of SIDS, it remains a leading cause of sudden and unexpected death in infants under the age of 1 in Western countries.

This includes infants who die suddenly from a known cause, such as suffocation, as well as those who die without a clear cause, such as from SIDS.

To test if there were something inherently different in SIDS babies, Dr.

Harrington and her colleagues compared dried blood samples from the newborn heel prick test of 655 healthy babies, 26 babies who died from SIDS and 41 babies who died from another cause.

They found that about nine out of ten babies who died of SIDS had significantly lower BChE levels than did the babies in the other two groups.

And because the Australian researchers did not have access to fresh blood samples for BChE, they did not measure absolute levels of the enzyme.

Some of the babies who died from SIDS had BChE levels within the same range as the babies who did not die?

Even if further studies helped fine-tune the test for BChE to accurately distinguish between babies who might die from SIDS and those who might go on to live healthy lives, doctors and parents would still be faced with a dilemma: What to do next.