Like many modern infants, my little son has a bit of a flat spot on the back of his head. It's the product of our conscientious efforts to put him to sleep on his back, in line with American Academy of Pediatrics recommendations for reducing the risk of Sudden Infant Death Syndrome.
Though the "back to sleep" guideline has been in place for years, and is well-supported by epidemiological data, no one has understood why it works. But new research may offer an explanation: an Australian study published online today in Pediatrics shows babies' brain oxygen levels are lower when they sleep on their tummies than when they are on their backs. The nadir in oxygen levels associated with tummy sleeping was seen in babies aged 2-3 months, at the age when SIDS risk is greatest.
The finding may be most significant for certain high-risk groups of infants, the authors add:
An important consideration is that impairment in cerebral oxygenation may be further exacerbated in infants at increased risk for SIDS, such as preterm infants and infants whose mothers smoked during pregnancy.
Preterm birth and maternal smoking can both adversely affect regulation of blood flow and oxygen delivery to the brain, they conclude.