In this case check with hospital staff for specific guidelines. Breastmilk looks thin and bluish-white. When refrigerated fat rises to the top, so shake gently before using. You may add fresh chilled milk to a container of breastmilk that you have in the fridge already. You can use either glass or plastic containers because with freezing some of the leukocytes and nutrients are destroyed anyway, therefore if your milk will be used within 8 days it's best to store the milk in the refrigerator.
Smaller amounts are also easier and faster to thaw and heat.
You can add fresh, chilled milk to a container with already frozen milk. When milk freezes it expands, so don't fill containers to the top, leave some room for expansion, don't tighten caps until milk is frozen. Always put a label with date on each container. 3-6 months in a refrigerator freezer with a separate door, store milk in the back of the freezer. You can thaw a container with frozen milk by holding it under cool running water and gradually add warm water until the milk is thawed and heated to room temperature.