Sudden infant death syndrome (SIDS) describes the sudden, unexplained death of an infant less than a year old. It is also called "crib death," but cribs do not cause SIDS.

Causes and Risk Factors

Nobody truly knows what actually causes SIDS.  Many healthcare providers and researchers believe SIDS is not a single condition that is always caused by the same medical problems. Rather, SIDS may be caused by several different factors as outlined by the American Lung Association.

• Some experts believe that SIDS babies are born with differences in their brains that make them unable to wake up from sleep when they are breathing high carbon dioxide or low oxygen levels; this leads to abnormal breathing or heart function.
• Researchers have found that infants who eventually died from SIDS had more trouble waking up during the night than other infants. Infants who died from SIDS also tended to wake up partially more frequently and for a longer period of time in the first part of the night and completely wake fewer times during the latter part of the night.
• Scientists are beginning to find differences in genes and DNA that may make infants more vulnerable to SIDS.
• SIDS may be a result of incorrect brain signals due to irregular brain chemistry.

Specific risk factors for SIDS have been identified. The most important are:

• A mother's smoking during pregnancy
• Placing the infant on its tummy to sleep, which can cause the baby to breathe in too much carbon dioxide and not enough oxygen
• Secondhand smoke in the home

Other risk factors include:

• Bed sharing with parents or others
• Soft bedding in the crib
• Multiple birth babies
• Male babies
• African-American babies
• American Indian/Alaska Native babies
• Premature babies
• Babies with a sibling who died of SIDS
• Mothers who smoke or use illegal drugs
• Teen mothers
• Short time between pregnancies
• Late or no prenatal care
• Poverty

Whom does SIDS affect?

Some babies are more likely to die of SIDS than others:

• Male babies more than female babies
• Premature and low birth weight babies more than full-term babies and those of normal birth weight
• African American and American Indian/Alaska Native babies more than babies of other races or ethnic groups
• Infants who share a bed with parents or others more than babies who sleep alone
• SIDS is most likely to occur in babies between two and four months old, and 90 percent occur by six months of age. SIDS occurs more often in winter months, with the peak in January.

How common is SIDS?

SIDS is the third-ranking cause of death for infants under one year of age. The overall SIDS rate has dropped throughout the United States, but there are differences among racial and ethnic groups. African American and American Indian infants are 2.1 and 1.9 times more likely, respectively, to die from SIDS than White infants.

Many SIDS deaths can be avoided by simply making sure that the infant always has access to fresh air. Everyone who cares for infants should know these simple steps:

1. Don't confine the baby so that it can't move its arms, legs and head.
2. Don't place the baby in a "protective" valley of pillows, blankets or clothing that might cause an 'air dam'.
3. Don't raise the heat in the baby's room (cool is just fine).
4. Check the baby often, and don't be afraid of entering baby's room in order to avoid waking him or her.
5. Introduce air currents in baby's room. A fan blowing up to the ceiling or against a wall can create gentle air currents in an open crib.
6. Have a source of fresh air that can enter the room -- open a window, or keep the door partially open.
7. Make sure window treatments don't obstruct the inflow of air. Always leave shades or blinds up a bit to let air in.
8. If bumpers are used, make sure there is space for the flow of air.
9. Bumpers should never be used in playpens.
10. Don't place baby in the middle of a multitude of toys and stuffed animals that might cause an 'air dam'.
11. Carriages and portable cribs with raised sides should never be used indoors.
12. Consider placing baby in an inclined sleeping position. Having the head in the up position lets exhaled air slide down to the feet.
13. Keep infants off the floor and at least two feet above the floor. Heavy gases can concentrate in the bottom of a room.
14. Be very cautious if you cook with gas, heat with gas, or use fireplaces, kerosene heaters, or when using a barbecue indoors. (Heating an apartment or house with a gas oven is very dangerous to everyone in the house.)
15. Homes with attached garages can be a source of harmful fumes in adjacent rooms when cars are left running.
16. Painting the inside of a house produces harmful fumes, as do cleaning solvents and furniture polishers.
17. Put off having rugs and furniture cleaned until the infant is at least 6 months old. Some carpet cleaning chemicals use carbon dioxide as the cleaning agent.
18. Postpone any home improvements until the infant is 6 months old to avoid large amounts of airborne dust.
19. Try to avoid having baby sleep in a basement. Heavy fumes tend to collect in them without an easy escape route.
20. New carpeting is another source of fumes that could be harmful to an infant.

The danger period for SIDS is primarily between two and four months. For the first two months of a baby's life, baby doesn't sleep long enough to reach a dangerous condition. After four months the baby is much larger and more animated during sleep. The 5 month old baby has then "grown out of" the danger zone for SIDS; however, there have been cases as old as eleven months. During the first six months, it is a good idea to always travel with a small fan with the diaper bag and never let down your guard.

SIDS Resources

SIDS Prevention online

American Lung Association

Mayo Clinic on SIDS

Centers for Disease Control and Prevention