Babies who are breastfed – especially those only fed breast milk, and not formula as well - are less likely to die of sudden infant death syndrome, or SIDS, suggests a new analysis of past studies.
While the findings can't prove that breastfeeding causes the lower risk of SIDS, the authors write in Pediatrics that other explanations seem unlikely.
"Breastfeeding is the best method of feeding infants," said Dr. Fern Hauck, the study's lead author from the University of Virginia School of Medicine in Charlottesville.
SIDS, also known as "crib death," is defined as a sudden and unexplained death - usually during sleep -- in a baby less than one year old. It's most common in infants between two and four months old, according to the National Institutes of Health, and kills about 2,500 infants in the U.S.each year.
Researchers aren't sure what causes SIDS, but they known that African American and male babies are more likely to die from SIDS, and that parents can cut down on their baby's risk by making sure infants sleep on their backs and don't get too hot.
One theory for the cause of SIDS, said Hauck, is that it happens in babies sleeping with their faces down or heads covered who don't turn their heads or cry like most babies would, and slowly suffocate.
Breastfeeding could be linked to SIDS because it protects infants against minor infections that have also been shown to make sudden death more likely, the authors note.
The World HealthOrganization, among other medical groups, recommends that mothers breastfeed their babies for the first six months of life.
In the new review, Hauck and her colleagues combined data from 18 studies that asked mothers of infants who had or hadn't died of SIDS about whether they breastfed the infants.
Combining the results, the researchers found that the rate of SIDS was 60 percent lower among infants who had any amount of breastfeeding compared to those who didn't breastfeed, and more than 70 percent lower in infants that been breastfed exclusively - without any formula - for any period of time.
That led the authors to conclude that any breastfeeding helps protect a baby against sudden death.
They note, however, that more research is needed to see if the duration of breastfeeding affects the risk of SIDS - specifically, if babies who are breastfed for longer get more protection that those who are only breastfed for a short time after birth.
The analysis doesn't definitively show that there's a cause and effect relationship between breastfeeding and SIDS risk, but Hauck said she is "fairly confident" that's the case.
"We found a protective effect even after controlling for factors that could explain the association," Hauck said. For example, the link remained even when the authors took into account the fact that women who smoke cigarettes are less likely to breastfeed, and also may be more likely to have an infant die from SIDS
Hauck added that along with breastfeeding, babies who sleep in the same room as their parents - but not in the parents' bed - and those who use a pacifier while sleeping also have a smaller risk of sudden death.
The findings, the authors write, underscore the importance of promoting the positive effects of breastfeeding for both moms and babies.