Layering Breast Milk
You may add “new” milk to previously chilled or frozen milk. Chill the new milk prior to adding it to the container of milk. The expiration date of that container of milk will be from the date of the original milk.
It is best to freeze milk in feeding-size quantities. If you are just starting to pump, you may not yet have an idea of what will be the right size for your baby. Freeze in 2- to 3-ounce quantities to start. You don’t want to thaw out more milk than your baby will take in 24 hours. You can always get more if necessary, but you will be dismayed if you have to discard pumped breast milk. After you have some experience with how much your baby takes from a bottle, you can freeze milk in that quantity.