Sudden infant death syndrome, or SIDS, has been recognized for hundreds, if not thousands of years. It is the leading cause of death for children between the ages of 28 days and 1 year. These tragedies happen when an apparently normal infant, generally two to three months of age, is put to bed, only to be found sometime later limp, not breathing, and to have no beating of his heart. Many times these infants are rushed to the hospital, where the doctors try to revive them. Most of the time we are unsuccessful. Or, if we do manage to get some return of heart rate, these unfortunate babies typically die several hours or a day or so later. I have been involved in dozens of cases like this during my career.
No one knows what causes the tragedy of SIDS. We do know that some children are at a higher risk than others. Known risk factors include these, among others:
- Being born prematurely or at a low birth weight
- Sleeping position
- Poor prenatal care for the mother
- Exposure to tobacco smoke
- Having a sibling or cousin die from SIDS
A good way to think of how these risk factors interact, called the “triple risk factor theory,” is shown in this diagram:
The idea is as follows. There is a critical time in early brain development when an infant’s brain learns how to regulate his breathing reflexes. When, during that critical time, an infant predisposed to get SIDS (such as from a family history of it), finds himself in an environment that affects breathing (such as tobacco smoke), the chances of getting it go up.
A large campaign begun in 1994, called “back to sleep,” has focused on the second of these SIDS risk factors in the list, sleeping position. There is an association between a baby sleeping prone — on his stomach — and SIDS. So we’ve stressed putting a baby to sleep on his back. And, probably because of this program, SIDS deaths have gone down, as shown in this graph. Although it’s an old statistical principle that correlation doesn’t prove causation, you can see that overall changes in infant sleep position and a reduction in SIDS cases correlate quite well.
So you can see we’ve made real progress in reducing SIDS. In 1990, before the “back to sleep” program, SIDS deaths were 126 infants per 100,000 births, or between 1 and 2 infants per thousand babies; only six years later the rate was half that. The graph below, however, shows that this positive trend has leveled off since then.
(Look at the middle line, the diamonds : the squares are unknown or otherwise mysterious deaths, and the top line, the triangles, are the two added together.)
One reason for this leveling off may be that, since 2001, the number of parents who put their infant to bed on his stomach has not changed — a recent survey indicated that about a quarter still do this, a number that has been unchanged over the past decade.
Looking at the data, the American Academy of Pediatrics recognized that, although a supine (on your back) sleeping position is important for reducing the risk of SIDS, there are other aspects of sleep position that also likely play a role in SIDS. This has led to a new set of recommendations for infant sleeping position. These include:
- Infants should be placed for sleep in a nonprone position. Supine (entirely on the back) confers the lowest risk for SIDS and is preferred. However, while side sleeping is not as safe as supine, it also has a significantly lower risk for SIDS than prone. If the side position is used, caretakers should be advised to bring the infant’s lower arm forward to lessen the likelihood of the infant rolling to the prone position.
- A crib that conforms to the safety standards of the Consumer Product Safety Commission is a desirable sleeping environment for infants. Although many cradles and bassinets also may provide safe sleeping enclosures, safety standards have not been established for these items. Sleep surfaces designed for adults may have the risk of entrapment between the mattress and the structure of the bed (for example, the headboard, foot board, side rails, and frame), the wall, or adjacent furniture, as well as between railings in the headboard or foot board.
- Infants should not be put to sleep on waterbeds, sofas, soft mattresses, or other soft surfaces.
- Avoid soft materials in the infant’s sleeping environment. These include such things as pillows, quilts, comforters, or sheepskins under the infant. Soft objects, such as pillows, quilts, comforters, sheepskins, stuffed toys, and other gas-trapping objects should be kept out of an infant’s sleeping environment. Also, loose bedding, such as blankets and sheets, may be hazardous.
- Overheating should be avoided. The infant should be lightly clothed for sleep, and the bedroom temperature should be kept comfortable for a lightly clothed adult. Over-bundling should be avoided, and the infant should not feel hot to the touch.
You can read more about the details, as well as about the rationale, the background science, for these new recommendations here.
There are some potential problems with back sleeping. One of them is getting a flat spot on the back of the infant’s head. This happens because an infant’s skull is so soft; if the back of the skull is always on a flat surface, it can make a dent there. There are various ways to prevent this, one of which is supervised “tummy time” for your infant.
When is it safe to let your child sleep on his tummy? A good, and quite sensible, rule of thumb is that when your child is able to roll back to front it is fine to let him end up in whatever position he likes best.