Donor breast milk that's screened, pasteurized and distributed through milk banks can protect preemies against serious illness, but donated milk bought online or obtained from friends can actually make babies sick, say U.S. pediatricians.

In its first policy statement on donor human milk, the American Academy of Pediatrics (AAP) advises against using internet-based or informal human milk sharing. These sources of human milk carry the risk of bacterial or viral contamination, or exposure to medications, drugs, herbs or other substances.

Most donor milk is distributed by milk banks through hospital neonatal intensive care units, and is typically reserved for preemies and other vulnerable infants. With limited supplies, some parents are obtaining donor human milk directly from other parents or from internet sources that may be less safe since they vary widely in screening of donors and methods of milk storage and transportation.

"We do not recommend direct milk sharing even if they have used home methods to try to pasteurize it," said Dr. Steven Abrams of Dell Medical School at the University of Texas at Austin, the lead author of the policy statement.

More on this...

"Milk banks are tightly regulated and use one of several well-established and proven methods of pasteurization to remove virtually all risks of transmitting infections," Abrams added by email.

Human milk offers advantages for all newborns, but particularly for infants weighing less than 1,500 grams (about 3.5 pounds), according to the AAP. Studies show infants fed human milk have lower rates of what's known as necrotizing enterocolitis, a life-threatening intestinal disorder that primarily affects premature babies, as well as a lower risk of lung and eye diseases.

Mother's own milk is always preferred, in part because some of breastmilk's beneficial biological components may be reduced after pasteurization.

But donor human milk can be an effective alternative when maternal milk isn't available or falls short of the infant's needs, according to the AAP. Reliably safe supplies of donor human milk from established milk banks are still limited, however.

Women who can't afford or access milk bank donations would be better off seeking help from friends than from the internet, said JoAnne Flagg, a researcher at the Johns Hopkins University School of Nursing in Baltimore, who wasn't involved in the policy statement.

It's possible to pasteurize donor milk at home using what's known as the Holder pasteurization method, which heats milk to 145 degrees for a half hour then gradually cools it, or by flash heating, Flagg said by email.

"Infant formula provides the nutrients the infant requires, but has no additional health benefits," Flagg said. "Donor milk a mother obtains from friends that is pasteurized by the above methods would be superior to infant formula."

But she cautioned that donor milk from the internet or that isn't pasteurized could not only expose babies to bacteria or viral contaminants, it might not even contain breast milk.

Because improperly unpasteurized milk can transmit infections, many clinicians consider home pasteurization unsafe and discourage it even when women get milk from people they know, said Dr. Valerie Flaherman, nursery director at the University of California, San Francisco Medical Center.

"Mother's breast milk provides the best and safest nutrition for babies," Flaherman, who wasn't involved in the policy statement, said by email.

"Buying milk from the internet and feeding it to babies is hazardous and risks giving the infant an infection, either an infection directly transmitted from an infected donor or an infection that occurs because milk storage conditions were poor," Flaherman added. "Formula is prepared and stored according to FDA guidelines and is a much safer choice than casually shared breast milk."