Breast-feeding, what many believe to be the most intimate act between a mother and child, is also generally believed to be an act exclusively between a mother and child.
According to experts, however, there is a growing trend of cross-nursing, in which a mother will allow another woman to breast-feed her baby.
"I think that it's just not been our social norm," said Morgan McFarland, who has been breast-feeding her friend Sarah Griffith's son since he was just 3 months old. "In some cultures, it is, and you would think nothing of, you know, nursing your neighbor's child if something happened, or nursing your sister's baby if she has to go to work."
To Lisa Moran, editor in chief of Babytalk magazine, the rising trend is not surprising.
"Cross-nursing is the logical extension to the rise in breast-feeding rates that we've seen in the past 15 years," she told "Good Morning America." "Moms are really committed to breast-feeding exclusively and finding new ways to do that. Cross-feeding, cross-nursing is one of those."
Not everyone sees cross-nursing so clearly, however.
According to a poll by Babytalk, 45 percent of people say cross-nursing is 'disgusting' or 'weird.'
McFarland believes some people have problems with an implicit "sexuality" connected to breast-feeding.
"They assume that anything that is to do with breasts has to be sexual," she said. "So, it's, I guess, bad enough if you're doing it with your own child. But then, you add another child to the mix and they're really concerned about it. It's silly."
Though it is seen by some as taboo, other experts have more practical concerns.
Leigh Anne O'Connor, leader of La Leche League International -- an organization that provides support to breast-feeding mothers -- warned parents that the milk their children gets from another woman should be screened for diseases, such as tuberculosis, syphilis, HIV and hepatitis-associated anitigens.
Rather than accepting milk from a friend, the La Leche organization recommends mothers try milk banks where the milk is screened and pasteurized.
But, for McFarland, cross-nursing is about more than the health risks and benefits.
"I think that a move back towards cross-nursing, or even just getting together with your nursing babies and sharing stories and becoming comfortable talking about the topic ... meets a very primal need for us -- that sense of bonding in the community."