The woman, who has not been named, shared a photo on a breastfeeding support page and explained what happened.
“In some weird chain of events today I ended up breastfeeding my sister’s son while she was away because he would not take the bottle his mumma pumped him,” she wrote on ‘Breastfeeding Mama Talk’ on 17 September.
“In return, because my son won’t latch and is strictly fed bottles I pump, I fed my son my sister’s perfectly good pumped milk, which made for two very happy and content babies.”
The Facebook page promotes positivity around breastfeeding, but several people posted negative comments on the post.
“Am I the only one who thinks this is seriously odd?” one person wrote.
Another person commented: “This isn’t safe for the baby. I would feel weird if my baby nursed from someone other than me. I think because we have such a great nursing relationship.”
After a series of negative comments were posted - some of which have now been removed - the Facebook page founder, Kristy Kemp, waded in.
“I’m not sure where on the post opinions were asked for,” she wrote. “Wet nursing is supported and encouraged here just like any other form of breastfeeding.”
She added: “I love how mad people get when I respond what I think about their opinions... Yet they felt good and able to comment their negativity on what they think about other people’s actions in the best interest of their babies.”
The most recent comments on the post have supported the woman in the photo and the act of wet nursing.
“This is literally the best thing I’ve read in a while! How awesome,” one person wrote.
One mum wrote: “My daughter was eight months when her cousin was born.
“My sister tried everything to get him to latch on but he didn’t want to. She tried bottle feeding him and nothing. The nurse saw me breastfeeding my daughter while I was visiting and asked if I was willing to breastfeed my nephew.
“I said yes and my sister didn’t mind. He latched on like a pro. I breastfed him for six months.”
Another wrote: “I’m a twin and while I went home to visit I nursed my sister’s son while she nursed mine. All the milk that I had pumped while I was visiting went into a bottle that my nephew drank because my son wouldn’t drink my milk once it had been frozen.”
The post was shared nearly 400 times within three days and received 600 comments.