How to keep track of your frozen breast milk stash and use the oldest bag first

Milk is pumped on many days and in many amounts, and the date is the only thing that tells you how long a bag has been stored. Labels rub off, bags get shuffled when someone digs for space, and a bag moved from the fridge to the freezer is easy to mislabel.

The result is usually one of two things: older milk sits at the bottom until it is past the recommended time, or the newest bag gets used first because it is on top.

The US Centers for Disease Control and Prevention (CDC) gives these general times for freshly expressed milk for healthy, full-term babies at home:

• Refrigerator, 4°C / 40°F: up to 4 days. If you will not use it within 4 days, freeze it.
• Freezer, −18°C / 0°F or colder: best within about 6 months, and up to 12 months is acceptable.
• Once thawed: use within 24 hours in the fridge, and do not refreeze it. Leftover milk from a feed should be used within 2 hours after the baby finishes.

The times count from the day the milk was pumped, not from the day it went into the freezer. Other health authorities publish slightly different numbers, so if your midwife or pediatrician gave you a sheet, follow that one.

1. 1Label every bag with the date pumped and the amount. If you pump more than once a day, add the time.
2. 2Freeze small portions, roughly one feed each, so you thaw only what you need.
3. 3Put new bags at the back or the bottom and take from the front or the top. Some parents keep one box per week, which makes the oldest box obvious.
4. 4If you combine milk from several sessions, label it with the earliest date.
5. 5Once a week, look at the oldest bags and plan to use them in the next few days.

Baton has a Milk stash screen for this. It is free, and it is a list of what you tell it: it does not read your freezer and it does not count down by itself.

1. 1Open More, then Milk stash.
2. 2Tap “Add a bag”. Set the amount, the day it was pumped (today by default, up to any earlier day) and where it is stored: Fridge, Freezer or Deep freezer. Then tap “Add to stash”.
3. 3The list shows bags with the oldest pumped first, plus the total number of bags and amount, overall and per place. Each bag has a “Use by” date calculated from the day pumped: 4 days for the fridge, about 6 months for the freezer and 12 months for the deep freezer.
4. 4Tap a bag to open it. You can move it to another place, mark it Used, or Discard it. A bag marked used or discarded leaves the list. Moving a bag keeps the pumped date, so the use-by date is recalculated from it.
5. 5A bag close to its date is labelled “Use soon”, and one past it is labelled “Past the guidance date”. On the Today screen a card appears when any bag is in one of those states, and it opens the stash when tapped.

The screen quotes the same guidance, with its sources: the CDC's “Proper Storage and Preparation of Breast Milk” and the Academy of Breastfeeding Medicine's Clinical Protocol #8. The “deep freezer” option refers to −20°C / −4°F or colder.

Be clear about the limits so the list stays trustworthy:

• Logging a bottle does not take a bag off the list. When you thaw and use a bag, tap Used yourself.
• The use-by date is general guidance counted from the day you pumped, not a safety check of the milk. Smell and appearance, and your own storage, matter too, and Baton cannot judge them.
• It does not know your freezer's real temperature or whether milk was thawed or warmed earlier.
• On a phone that joined as view only, such as a grandparent's, the stash can be read but not changed.

Each bag is an entry in the baby's log, which both parents share through their own iCloud accounts, so a bag added on one phone shows up on the other once both are online. The partner who fills the next bottle can open the list and see which bag is oldest, and tap Used when it is finished.

Because the list only changes when someone taps, agree on one habit: whoever thaws a bag marks it used straight away.

Ask your pediatrician, midwife or a lactation consultant if you are unsure whether a bag is still fine to use, how to thaw and warm milk for a premature or ill baby, or how long to store milk in your situation. If a bag looks or smells wrong, do not use it.