Mothers who struggle to breastfeed their children are finding donors on social media.
Informal milk sharing, as it's known, is a growing trend - with one group boasting more than 18,000 members.
In these groups, women who require extra breast milk can ask for support from other mothers who have surplus milk.
But it's not regulated, and women can only use their judgement as to whether the milk they are feeding their baby is safe.
Rebecca Poole started using a milk donor because she wasn't producing enough to feed her son, Theo.
The mother-of-two, who is from Wolverhampton, didn't want to use formula and stumbled across a milk sharing group after a quick online search.
Unlike on some websites where women charge for the milk (one woman advertised 250ml of breast milk for £2.50), Rebecca doesn't exchange any money with her donor.
As with Rebecca's donor, some women who choose to donate their milk via social media also donate to neonatal milk banks.
There are 17 of these milk banks in the UK, including one at Birmingham Women's and Children's Hospital.
Gemma Holder, who works at the milk bank, says the biggest risk for parents who use informal milk donors is how the milk is stored.
At the minute, milk banks are used for sick and premature babies.
But Rebecca would like to see more milk banks for mothers who are struggling to breastfeed their baby.
- What do you think? Join in the conversation on our Facebook page.