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And when mice were injected with these human blood stem cells in the lab, the cells were found to be good at making red blood cells - a positive sign, Dr Encabo said.

"You are not just helping people with your red blood cells – now the plasma in your blood donation is helping people too."

The condition occurs at pregnancy when the mother's red blood cells are incompatible with that of their growing baby.

It is caused by genetic change that means people make haemoglobin - a key protein in red blood cells - that doesn't work properly.

The effect of haemodialysis is said to mimic the effect of carbon dioxide in the blood – which increases the pH or alkalinity inside red blood cells.