Breastfeeding and babies' lives.

Although infant mortality is low in the United States, recently published research suggests it could be still lower if more mothers breastfed their babies. The study, conducted by NIEHS epidemiologists Aimin Chen and Walter Rogan and published in the May 2004 issue of Pediatrics, also indicates that prolonged breastfeeding may foster an even greater reduction in infant mortality.

The researchers drew data from the 1988 National Maternal and Infant Health Survey for their case-control study of breastfeeding and its relationship with infant survival. The survey, conducted by the Centers for Disease Control and Prevention, provided information about breastfeeding and other variables for 1,204 infants who died at age 1-12 months of causes other than birth defects or cancer, and 7,740 infants who survived at least 1 year.

According to Chen and Rogan's analysis, breastfed babies were 21% less likely to die between ages 1 month and 1 year, and those breastfed at least 3 months had a 38% reduction in mortality by age 1. Breastfeeding appeared to reduce mortality regardless of cause of death--infection, injury, sudden infant death syndrome, or other/unknown causes. Interestingly, traumatic injury--related deaths appeared to be the most reduced by breastfeeding, with a 41% reduction.

"[Fewer] traumatic injury deaths was very interesting to me," says Nancy Wight, a neonatologist and medical director of lactation services at Sharp Mary Birch Hospital for Women and Children's Hospital in San Diego. "That was something that I hadn't really thought of before, but it makes sense. Breast milk is important, but it may be simply part of a parenting package that is overall child-protective. Causality is hard to ascertain; there are many different factors that go into breastfeeding."

Jacqueline Wolf, an associate professor of social medicine at Ohio University in Athens, agrees: "I think what the researchers propose is that very possibly breastfeeding mothers are more in tune with their babies, spend more time with them, and watch them more closely. Other researchers have suggested that the hormones prolactin and oxytocin, associated with lactation, might be responsible in part for more attentive parenting. It's hard to untangle cause and effect here."

According to Wight and Wolf, the relationship between breastfeeding and infant mortality might have been dearer if Chen and Rogan had been able to work with more detailed breastfeeding data. "If they had been able to study the effect of breastfeeding exclusivity and duration, and not just initiation rates, my educated guess is that they would have seen even greater correlation between amount of breastfeeding and reduction in infant mortality," says Wolf.

Nevertheless, both Wolf and Wight view this study as a valuable addition to the case for breastfeeding. "It simply reinforces what mothers have known for thousands of years: breastfed babies survive," says Wight.

Wight also indicates that the study serves as a reaffirmation of the need for breastfeeding in an industrialized society. "A lot of physicians and others say [breastfeeding] is fine for the Third World, where they have very high risk of infection and infant mortality anyway, but in the United States we have good formulas, a clean environment, and good health care, and it doesn't make a difference," she says. "This shows very dearly that [breastfeeding] does make a difference."