Your expressed breastmilk is a unique fluid, a combination of both nutrition and antibodies, which protects your baby against illness and promotes proper growth and development. Expressed breastmilk can be thought of as a fresh, living substance; it is more than just a food. Therefore, you will need to take good care of the milk you pump, as how it is stored will affect how well the nutritional and anti-infective qualities are preserved. Follow these guidelines to safely collect and store your breastmilk.
Milk Storage Guidelines
- Hard-sided containers, glass or plastic, protect your milk, and are a one-time expense. However, they are bulky and can take up a lot of room to store. Research has shown that there is less fat loss with glass or plastic bottles. Look for BPA-free bottles. Any bottles you choose should have well-fitting, airtight, solid tops. Not all hard-sided containers are a universal fit for various breast pumps, so check carefully before buying. Expressing your breastmilk directly into the feeding container greatly decreases the likelihood of contamination.
- Plastic (polyethylene) milk storage bags, made for freezing and storing human milk, are convenient and take up less room for storage. However, they are a one-time use product and cannot be reused, and they are expensive. They can be attached directly to the breast pump for easier collection and storage in the same container. However, pouring milk out of them into a bottle can be awkward if they don’t have a pour spout. Moving the milk between storage and feeding containers also increases the possibility of contamination. Fat loss is higher in milk storage bags than hard-sided containers.
- Disposable plastic nurser bags or liners for bottles should not be used for storing expressed milk. They are not as durable, are prone to bursting or tearing, are not designed for freezer use, and are not designed for long-term storage. If you choose to use them, double-bagging can help prevent accidents. Never use plastic sandwich bags for storing breastmilk.
- Do not fill either hard-sided containers or milk storage bags more than three-fourths full to allow the milk to expand as it freezes. If you express into bottles, leave the cap loose before freezing, and then tighten once the milk is frozen. Squeeze out the air in milk storage bags before sealing. This also helps to prevent freezer burn and your milk from absorbing the odors from other foods.
- Label every container of milk with the date of expression and your baby’s name, using a sticky label or non-toxic marker. Labeling ensures that your baby gets your milk at childcare.
- Many mothers find a rack, such as the Mother’s Milk Mate Breast Milk Storage System® for storing bottles of milk (it dispenses bottles from oldest to freshest), or a plastic container, such as a bin or box to hold the bags of frozen milk (to prevent them sliding around and tearing), to be helpful. Make sure to mark the larger container with the month and year of milk collection (August 2010 #1, August 2010 #2).
- Store expressed breastmilk in ‘feeding sized’ quantities (two to four ounces) to minimize waste and make thawing easier. Some mothers use an ice-cube tray to freeze their milk. A new take on the old stand-by of using an ice-cube tray is MilkTrays®, a reusable, BPA-free, medical-grade plastic tray that freezes breastmilk in one ounce ‘sticks.’ It holds up to eight sticks (that fit in the mouth of bottles) and comes with a lid.
- It is fine to “layer” or combine milk from different pumping sessions on the same day. You can add freshly expressed milk to frozen milk after chilling it in the refrigerator (or cooler compartment) for at least 30 minutes. Avoid adding more freshly expressed milk than the amount already frozen in the container.
Milk Usage Guidelines
Your freshly expressed breastmilk should be given to your baby as soon as possible to have the maximum benefit. The vitamin content of expressed breastmilk degrades and the bacteria count increases the longer it is stored. Fortunately, breastmilk is full of immune properties that help to prevent bacteria from multiplying. Refrigeration of breastmilk preserves most of the immune properties, but not all of them. And freezing destroys the white blood cells that protect against illness, but preserves some of the other immune properties. No matter, expressed breastmilk that is properly collected and stored is still far superior to formula. Follow the guidelines below for best practices when storing your expressed breastmilk:
- Room Temperature – It is best if you can provide freshly expressed breastmilk to your baby. Antioxidant activity in breastmilk, important for fighting infection and mopping up free radicals, has been shown to decrease slightly with both refrigeration and freezing. If possible, pump once in the morning before work, and leave that bottle of freshly expressed breastmilk in the diaper bag for the first feeding at daycare. Should you forget and leave a bottle of freshly expressed breastmilk sitting on the counter or table, it will remain safe to use for four to six hours at temperatures up to 77°F or 25°C.
- Insulated Cooler – If you don’t have a refrigerator at work (or don’t feel comfortable leaving it in the workspace refrigerator), freshly expressed milk can be kept cool in an insulated container with freezer gel packs or ice packs when no refrigeration is available for up to 24 hours at 59°F or 15°C.
- Refrigerated – Refrigerated milk is next best, if at all possible. Always place your expressed milk in the coldest part of the refrigerator, usually at the back, away from the door. Freshly expressed milk can be refrigerated for three to eight days at 39°F or 4°C. If you do store your milk in a refrigerator at work during the day, or your childcare provider has questions about storing your milk around other food, you can let them know that the Centers for Disease Control and the U.S. Occupational Safety and Health Administration have both made statements that human milk is not a body fluid that requires special handling or storage in a separate refrigerator as a bio-hazardous material. It can be stored in a common refrigerator at work and childcare facilities.
- Frozen – If you know you won’t be using your refrigerated milk within three to eight days, it needs to be frozen as soon as possible after collecting. Place containers of breastmilk at least an inch away from the walls of a self-defrosting freezer to prevent defrosting and refreezing. Do not store containers in the door of a freezer where the temperature fluctuates. Always maintain a temperature of 0° F or -18°C. Frozen breastmilk will remain safe to use for three to six months in a self-contained refrigerator/freezer unit. You can store your milk in a deep freezer for 6-12 months at -4°F or -20°C. When using frozen breastmilk, always use the oldest stored breastmilk first. Try to rotate in a few frozen bags per week (two to four), along with your refrigerated supply, and freeze some of the freshly expressed milk to replace the milk you defrost. This ensures that your milk is rotated, and your baby still receives mostly fresh milk at feedings.