In the past, research has linked breastfeeding with prevention of Sudden Infant Death Syndrome (SIDS), but a new German study published in the journal Pediatrics has found that infants who are formula-fed are twice as likely to die of SIDS than breastfed infants.

The German Study of Sudden Infant Death examined the cases of 333 infants who died of sudden infant death syndrome along with 998 age-matched controls, between 1998 and 2001.

A total of 49.6 percent of cases and 82.9 percent of controls were breastfed at two weeks of age. Exclusive breastfeeding at one month of age halved the risk of SIDS; partial breastfeeding at the age of one month also reduced the risk, but after adjustment this risk was not significant. Being exclusively breastfed in the last month of life or before the interview reduced the risk, as did being partially breastfed.

SIDS is the leading cause of death for infants in developed countries, and yet the causes are not fully understood. While previous research has documented the relationship between breastfeeding and low SIDS rates, there was speculation that the relationship may have more to do with socioeconomic status, smoking or other lifestyle issues. So in this study, researchers adjusted the data to control for the effect of socioeconomic status.

They also suggested a mechanism that could explain a causal relationship between breastfeeding and SIDS-prevention. Most infants who die of SIDS are between two and four months old. At this age, maternal acquired immunoglobulin G is low and the infant has not yet begun to produce large amounts of its own immunoglobulin. Breastmilk contains immunoglobulin and cytokines, which may help stave off infections which are believed to contribute to SIDS. It has also been shown that breastfed infants are more easily aroused than formula-fed babies, another mechanism which could help prevent SIDS.

After the age of four months, infants are at a lower risk for SIDS and the older they get, the more their risk declines. Because the risk is so low by six months of age, researchers recommend that all babies be breastfed until six months of age.

For the full study visit the Pediatrics journal website.

Wendy Priesnitz is the founder and editor of this website, and co-founder and editor of Natural Life Magazine. She is the author of nine books about unschooling, natural parenting and green living. Read her blog.