Information about expressing and storing milk
Unfortunately, there is no clear answer to this question as there is no research about whether it is safe or not. Until recently, the standard answer was to discard any breastmilk left in the bottle after a feed. However, recently it has been suggested that it might be okay to store breastmilk in the fridge for a short time. The current thinking is that bacteria growth is possible, but not likely, because fresh breastmilk has anti-bacterial properties, and a breastfed baby has a strong immune system to deal with any bacteria that do grow.