And had the mother (and father) known a bit more they could have intervened too and just got in some formula
My fifth DC ended up losing 11% of her birthweight by ten days, and it was only because I inadvertently turned up for a pediatrician appointment for her a week early (US practice) that this was caught before it turned out to be a very serious problem for her.
I had four previous successes establishing breastfeeding under my belt. I knew how to breastfeed. All my older four babies knew how to do it too. DC5 whom I thought was doing fine was not doing fine. I was doing everything I had done with the others. She didn't have tongue tie, or thrush. Her latch was ok. She just wasn't using her tongue effectively, as far as anyone can guess.
She was producing wet diapers - not soaked but a little wet. She pooped, but there is a huge range of normal for that. If DC5 had not been seen and the issue turned around at ten days I suspect I - 37 years old and a mother of five - would not have identified a problem until it was too late.