New mothers are sourcing breastmilk for their babies from strangers. Is this a dangerous trade?

One Facebook group where parents share breastmilk boasts 10,000 members
Sarah Simpkins
Dr Briony Andrew.

After struggling to express milk for her three-month-old baby, an Australian woman turns to Facebook to ask mothers if they have any to spare.  

The Facebook group is called Human Milk 4 Human Babies.