Photo of mom breastfeeding friend's child ignites controversy

PHILADELPHIA -- A photo of a Pennsylvania woman breastfeeding a boy who isn't her own child is igniting a firestorm of controversy.

The photo shows Jessica Colletti breastfeeding her son and the son of her friend, Charlie Interrante.

Interrante, 25, said she wanted to breastfeed her son, but she couldn't do it herself and couldn't pump at work. That's when Colletti stepped up to the plate.

"How did you make the decision to have Jessica nurse Mateo?" asked ABC's Rebecca Jarvis.

"I was at my wits' end and when she offered, I was just nothing but thankful for it," Interrante said.

Colletti, 27, said she had never nursed another person's child before but said it felt "very natural."

"He was just another baby that was hungry," she said.

Some people posted online comments applauding the moms, but others condemned their decision. One comment read, "I found this picture disturbing," and another read, "Nothing wrong with breastfeeding, but why not cover up? Besides these two children are old enough to eat solid foods."

The concept of using a wet nurse is not a new one. The World Health Organization lists milk from a healthy wet nurse or human milk bank as the best alternative to milk from an infant's own mother.

"Of course, there's a risk with anything you do that's not the biological mom's breast milk, but if the woman has been screened, if she's healthy, if she is substance free, if her child is healthy as well, it shouldn't be a problem," said Kathleen McCue, a nurse practitioner and board-certified lactation consultant in Bethesda, Maryland.

The two women not only describe their sons as "milk brothers," but they have since moved under the same roof. Interrante moved in with Colletti and her husband two months ago.

Interrante said she is comfortable with Colletti breastfeeding her son as long as he would want to nurse.

ABC News contributed to this report.