For new parents, perhaps their greatest fear is that their precious newborn will stop breathing and die during the night. Although rare, sudden infant death syndrome, or SIDS, still strikes two out of every three thousand children born in the United States, and ranks as the leading cause of death among children one month to a year old.

Fortunately, parents can take a number of measures to guard against SIDS, such as positioning babies on their backs at bedtime. But such preventive measures only lessen the threat of SIDS. The biologic basis for the syndrome has remained unclear.

Until now. Writing in the Journal of the American Medical Association, researchers at Children’s Hospital Boston identified abnormalities in the brainstems of thirty-one children who died from SIDS. Their focus was on the medulla oblongata [meh-DOO-lah ob-lon-GA-tah], a primitive part of the brain that regulates basic functions like breathing, blood pressure and arousal from sleep.

As they sleep, babies can re-breathe their own exhaled air, increasing levels of carbon dioxide. When these levels get too high, the neural brainstem prompts a normal baby to wake up and breathe faster to take in more oxygen. In SIDS babies, the researchers believe, defects in nerve cells can impair this reflexive response.

Much work needs to be done. But this initial theory of the biology of SIDS offers hope for the development of a diagnostic test… one that would identify those at greatest risk and lead to medications to protect children with abnormal brainstems.