You could, but it is risky. Reheating breast milk twice means you could be losing twice the nutritional benefit, as some types of heating can destroy some key nutrients found in the milk. Moreover, the more you allow the breast milk to sit, the more likely it is to breed bacteria. This is especially true if you’re thawing, refrigerating, warming, and refrigerating again. We advise you simply thaw or chill any breast milk in the fridge and warm it once, whenever baby is ready to eat.