Researchers on Thursday said sighs, which healthy babies take every 50 to 100 breaths, help reopen parts of the lung, especially tiny airways prone to collapse.

But the team of researchers at the University Children's Hospital in Bern, Switzerland, and in Perth, Australia, wanted to know if sighs do more.

They studied 25 healthy one-month-old infants while they were sleeping in a crib or in a parent's arms, checking the heart rate and blood oxygen saturation as well as other breathing-related factors.

Writing in the Journal of Applied Physiology, David Baldwin and colleagues say they found that sighs are a mechanism for improving the neurological control of breathing.

Just before a sigh, an infant's breathing becomes just a bit too regular. The sigh adds some healthy variability to the breathing pattern, the researchers said.

They noted that sick and premature infants seem to sigh more often than healthier babies. They may be struggling to reset their systems.

The researchers say it may be possible to use breathing patterns to identify those premature infants who are most at risk for problems of abnormal breathing control, including sudden infant death syndrome – also known as crib death.