Back to Sleep: The Best Bedtime Position for Baby

In 1974, Congress passed the Sudden Infant Death Syndrome Act in an effort to discover what was causing the devastating and seemingly inexplicable deaths of otherwise healthy infants while they slept. More than two infants for every thousand born were dying this way every year. Thanks to research by the National Institute of Child Health and Human Development (NICHHD) and others, a correlation was soon seen between sleeping on the stomach and increased rates of sudden infant death syndrome (also called SIDS, or "crib death" in the past).

By 1991, the research was convincing enough that the American Academy of Pediatrics (AAP) was recommending back sleeping. And in 1994 the NICHHD and the AAP pushed a full-on national public health education campaign called Back to Sleep. Since that time there has been a remarkable 50 percent decrease in the incidence of SIDS, according to the AAP. "Other countries with similar campaigns have had similar success," notes pediatrician Karen Sadler, MD, yet the AAP and NICHHD report it is still the leading cause of death after the immediate postnatal period. "Ninety percent of infants who die of SIDS are under six months of age; most are between three and five months old," Sadler adds. "Neither do we know why this is the most vulnerable age."

For those still looking for a more definitive answer to why Baby should sleep on his back in order to prevent SIDS, there are a few likely explanations but no decisively certain one. We do know for sure that the statistical link between back sleeping and lower SIDS rates exists. Most of the explanations pertain to infant breathing. For example, when sleeping on her front, Baby is more likely to create a little pocket around her nose and mouth that traps the exhaled carbon dioxide, which is then re-breathed, reducing oxygen in her system to lethal lows. Similarly, heavy blankets or plush toys could cause this same CO₂ poisoning, especially when Baby has her face against the fluffy stuff. Another explanation is that back sleeping helps keep airways more open.

Overheating may be a contributing factor. So skip the blankets and put Baby in an adorable sleep sac outfit or gown with a drawstring bottom and hand covers if you live in colder climes. Keep the room comfortable for a lightly clothed adult. Smoking in the household or by the mother before birth is also linked to sudden infant death syndrome. So for this and a thousand other reasons, quit smoking as soon as you think of conceiving.

One key point is that babies should sleep on their backs every time they sleep, whether for the night or just while napping, and all caregivers who take care of the child should know this. The rate of SIDS among back sleepers who were then put on their stomach to sleep is a scary 18 percent higher than the usual rate.