At the same time, he credits the large amount of breastfeeding research going on with positive policy changes.
"Already across the country, we find that states are passing laws to protect mothers who are breastfeeding," said McKenna. "These things are making it possible for mothers to adapt these practices."
Breastfeeding typically has been a difficult area to research.
"There is some research that suggests a benefit [to breastfeeding]," said Rebecca Goldin, an associate professor of mathematical sciences and director of research for the Statistical Assessment Service at George Mason University.
At the same time, she said, it becomes difficult to draw wide conclusions because the studies typically are not randomized -- where women wouldn't be able to decide for themselves whether to breastfeed or not. As a result, researchers have to take into account any factors that might affect a woman's decision to breastfeed.
That may be why, for example, Goldin said, women who breastfeed tend to have fewer accidental deaths among their children -- simply because women who choose to breastfeed may be more attentive mothers.
But as to the Pediatrics study, Goldin said the $13 billion cost savings it estimates is not useful.
"It would take a lot of social and medical support to make that happen," she said, including support from nurses and possibly keeping women in the hospital longer.
But other costs would be higher.
"Probably, many of the costs to get breastfeeding that high would be social, not medical expenses," she said, including compensating employers for giving women time to breastfeed and having social workers visit homes to help new mothers with nursing.
"Those are very real costs," said Goldin. "When you do an economic comparison, it's unfair to only look at one aspect of the cost for any one particular decision. It's not clear that this is a fair savings to the nation."
But, Goldin said, studies like the current one present a problem for women who can't afford or otherwise choose not to pay those costs of breastfeeding, because often they are looked upon poorly.
"One of the risks of these kinds of studies is that they perpetuate that," she said. "I think it's perfectly within the realm of risks we take every day to decide not to nurse."
She asserted that driving could be made to look equally bad, given the medical costs in the form of car accidents.
"Is it fair to look at the medical costs of driving and talk about the morality of driving?" she said.
However, she agreed with other researchers that women who want to breastfeed should be able to.
"I think that women should get support for breastfeeding. I think that it shouldn't be so difficult to do it for women," said Goldin.
While she emphasized the benefits of breastfeeding, Beard agreed that when women can't breastfeed, there are acceptable substitutes.
"Without question, breastfeeding has some specific maternal and infant benefits," she said. "Although breastfeeding is absolutely ideal, for the mothers who cannot and choose not to breastfeed, infant formula is what's recommended. I don't want to beat her over the head with guilt. I let her know that infant formula is the safest, most nutritious and only recommended alternative to her milk."