SIDS is the sudden, unexpected death of a baby less than 1 year old with no explanation from a thorough investigation. The new study, published in the Annals of Epidemiology, shows:
Premature babies died of SIDS up to six weeks later than full-term babies, on average.
Babies born small for their gestational age had a higher SIDS risk than appropriate-sized infants.
The researchers included Donna Halloran, MD, MSPH. She worked on the study while a pediatrician at the University of Alabama. Halloran is now an assistant professor of pediatrics at Saint Louis University's medical school.
Doctors "must remain vigilant and, particularly for preterm infants, should provide SIDS prevention counseling beyond the first six months," Halloran and colleagues write.
SIDS and Premature Babies
Data came from U.S. birth and death records from 1996 to 1998. Nearly 11.4 million babies were born in the U.S. during that time. SIDS killed 8,199 of those babies, the study shows.
Premature babies typically died of SIDS later than full-term babies. Here are the babies' average ages when SIDS struck:
Full-term babies: 14 weeks after birth
Premature babies born at 28-32 weeks: 15 weeks after birth
Very premature babies born at 22-27 weeks: 20 weeks after birth
The average age at SIDS death was similar for babies born slightly prematurely (at 32-38 weeks of gestation) and full-term babies.
SIDS deaths were most common among babies born to women who were black or Native American, had low levels of education, were younger than 20, were unmarried, had five or more previous births, smoked, or drank alcohol. SIDS rates were also higher for baby boys, premature babies, and infants born small for their gestational age.
SIDS and Small Babies
The researchers checked the babies' size -- particularly, whether babies who died of SIDS were bigger, smaller, or average in size for their gestational age.
Babies who were small for their gestational age were 1.7 times more likely to die of SIDS than babies of average size for their gestational age. The timing of those SIDS deaths didn't differ much.
Babies born large for their gestational age were 30% less likely to die of SIDS than babies of average size for their gestational age.
Premature and very premature babies spend more time in the hospital before coming home. Their SIDS deaths typically happened several weeks after coming home, the study shows.
The researchers can't explain any of the SIDS deaths. The home environment could have an effect, or the slower development of premature babies may delay SIDS, they note.
Regardless of whether a baby is born big or small, early or late, parents and caregivers can take steps to help prevent SIDS.
Don't cover babies with extra blankets or clothes in the winter.
Always place your baby on his or her back to sleep -- for naps and at night.
Place your baby on a firm sleep surface, such as on a safety-approved crib mattress, covered by a fitted sheet.
Keep soft objects, toys, and loose bedding out of your baby's sleep area.
Do not smoke or allow smoking around your baby.
Don't share your bed with your baby during sleep. Keep your baby's sleep area close to, but separate from, where you and others sleep.
Consider offering a clean pacifier when placing your baby on his or her back to sleep.
Don't let your baby overheat during sleep.
Avoid products that claim to reduce SIDS risk; the effectiveness and safety of these products have not been thoroughly tested.
Don't use home monitors as a way to reduce SIDS risk. There is no proof that these monitors decrease the occurrence of SIDS.
Reduce the chance that flat spots will develop on your baby's head by providing "tummy time" when your baby is awake and someone is watching, changing the direction that your baby lies in the crib, and avoiding too much time in car seats, carriers, and bouncers.
Parents shouldn't share a couch with a baby during sleep.
SOURCES: Halloran, D. Annals of Epidemiology, Jan. 20, 2006; online edition. WebMD Medical News: "SIDS Cases Rise During Winter." WebMD Medical News: "New Tip to Help Babies Avoid SIDS." News release, Saint Louis University.
Reviewed by Ramaz Mitaishvili, MD