Sudden infant death syndrome (SIDS) is often attributed to babies' poor sleeping conditions like sleeping on soft mattresses and sleeping on their bellies instead of on their backs. However, a new study conducted by researchers from Boston Children's Hospital and Dana-Farber Cancer Institute shows that there are many other factors that increase the risk for SIDS besides sleeping environment.

Taking data collected from 1983 to 2012, the researchers reported that the number of SIDS cases has dropped by 71 percent, with much of the decline happening between 1994 and 1996 at the height of the Back to Sleep campaign. They acknowledged that the campaign was a major influence in reducing SIDS incidents.

However, they also identified other factors that increased babies' vulnerability to SIDS. These include poor prenatal and neonatal care, women's exposure to smoking during pregnancy, babies being born prematurely and teen pregnancy. Improvement in these areas lessened the risk for SIDS. Breastfeeding was also seen as a factor that lowered the babies' risk for SIDS.

"This study raises the question of other factors being critical in declining SIDS rates, not just sleep environment. Efforts to understand the biologic vulnerabilities of these infants are important," Dr. Richard Goldstein, a pediatrician at Boston Children's Hospital and lead study author, said in a press release.

Goldstein said providing safe sleeping environments for babies is important, but "improving overall maternal and infant health" should be emphasized. He also stressed the need to study biological factors that could influence SIDS, such as an impairment in the brain function that normally wakes babies up when they don't have enough oxygen.

The study was published online Dec. 2 in the journal Pediatrics.