Breastmilk: Pumping, Collecting, Storing

The following are general guidelines for collecting and storing breastmilk when using a hospital-grade electric breast pump. If the neonatal intensive care unit (NICU) gives you more specific instructions, follow their recommendations.

Getting ready

Before you begin to pump, read the instruction manual for the breast pump and collection kit you are using.

Keep it sterile

Breastmilk is not sterile, but you do not want to introduce "outside" bacteria when getting ready to pump, during pumping, or when storing milk or transporting it to the NICU.

  • Always wash and rinse your hands thoroughly before handling any clean pump parts, your breasts, or the milk collection bottles or containers.

  • Certain pump collection kit parts must be cleaned and sterilized according to the instruction manual. Most recommend thorough cleaning of these parts after each use and sterilizing parts at least once in 24 hours.

  • The collection bottles or containers that attach to the pump and are used to collect and store your milk should be sterile (boiled or steamed). The NICU may be able to supply the milk collection containers.

Try different settings

You may have to try different methods and settings on the breast pump before you find ones that work best for you. The following are some general tips:

  • You can moisten the rim of the breast flange before pumping if you want to create a better seal on the breast.

  • Some mothers prefer to center the breast flanges on the nipple and areola first and then turn the pump on. Others turn the pump on first and then place the flanges over the breasts.

  • Start the pump at the low or minimal suction setting. Gradually move the setting to increase the level of suction. The level usually is set as high as comfort allows. Decrease the suction if it causes discomfort.

  • Suction can't be maintained if the seal of the flange on the breast is broken, so check the seal of the flange periodically. Also watch for the rhythmic pull and release of the nipple and areola within the flange.

  • Expect to pump for a few minutes before you see a steady flow of milk.

  • Don't fill collection bottles more than two-thirds full so that milk does not flow back. This also allows the milk to expand if it is to be frozen. If you easily fill bottles, have more collection bottles ready. Stop and change bottles as needed. If your baby takes more than the amount in one bottle at a feeding, you might attach collection bottles that can hold a larger amount to the breast flange.

  • When you are ready to stop pumping, use a clean finger to press in on your breast just above the pump breast flange. This should break the seal between the flange and the breast tissue. If milk has pooled in a flange, tilt it so that milk can drain into the collection bottle as you remove the flange. Then turn off the breast pump. Some mothers turn the breast pump off first, and then break the seal between the flange and the breast.

Storing your breastmilk

Combining milk

If you pumped both breasts at once and the total amount of milk will fill one bottle no more than two-thirds full, you may combine the contents in one bottle by carefully pouring the milk from one sterile container into the other. Don't combine milk from different pumping sessions when pumping for a high-risk baby.

Label the collection container(s) right away

Labels should include the baby's name, the date, the time of day pumped, and any medicines or substances, such as cigarette byproducts that you have taken or been exposed to since the last pumping session.

  • If using unrefrigerated, fresh breastmilk, it should be fed to a baby within an hour of being pumped. Don't leave milk out longer than 30 to 60 minutes when it is to be given to a high-risk baby. This risks contamination—something a high-risk baby does not need.

  • It is not always possible to give a baby fresh breastmilk. Or you may get more than needed for a feeding and want to save the milk for later use. In these cases, refrigerate your milk in the labeled collection bottles right away. The refrigerator should be at a temperature of 32°F to 39°F (0°C to 3.9°C).

  • Freeze labeled collection bottles if the milk will not be used within 24 to 48 hours. The NICU staff will let you know whether they are using 24 hours or 48 hours as a guideline.

  • Don't freeze breastmilk that has been refrigerated for more than 24 to 48 hours. Although milk has been shown to be safe when refrigerated for several days, experts usually recommend freezing milk sooner when it is to be given to a high-risk baby.

  • Freeze breastmilk in small amounts so that only what your baby needs is thawed each time. After breastmilk has been thawed, it must be used within 24 hours (if thawed in the refrigerator), or 4 hours if it was warmed, or it must be discarded. Your baby's nurse can help you to know how much your baby needs daily.

Frozen breastmilk may be kept:

  • Up to 2 weeks if the freezer compartment is within the refrigerator. You must open the refrigerator door to reach the freezer with this model.

  • 3 to 6 months in a freezer that is part of a refrigerator unit but has a separate door

  • 6 to 12 months in a separate, 0°F (-18°C) "deep" freezer

Transporting refrigerated or frozen breastmilk

Place it in an insulated bag or cooler with a cool pack. The farther you live from the NICU, the more likely it is that you will have to pad the inside of the cooler with extra cold packs to keep frozen milk from thawing.

Fresh breastmilk

Fresh breastmilk contains the most active anti-infective properties. Refrigerated breastmilk has fewer anti-infective properties than fresh milk, and frozen breastmilk has the least.

Thawing breastmilk

The following are general guidelines for thawing frozen milk:

  • The oldest milk should be used first, unless recently expressed milk is recommended.

  • Thaw breastmilk by placing the collection container in the refrigerator. If you need the milk more quickly, you can hold it under warm, running water or place it in a cup, pot, bowl, or basin of warm water.

  • Don't thaw breastmilk at room temperature, in very hot water, or in the microwave. Microwaving can create hot spots. Both microwaving and heating in very hot water may decrease the amount of certain anti-infective properties in the milk.

  • Your milk separates during storage, and the cream rises to the top. Gently swirl, or rotate, the collection bottle of milk to mix it together. Don't shake it vigorously.

  • Don't refreeze milk once it has been thawed. Thawed milk must be used within 24 hours for a baby in the NICU. (It is safe to give milk that has been thawed for 24 to 48 hours after the baby is home.)

Taking care of your breast pump and collection kit

It is important to maintain the breast pump and collection kit in good working order:

  • Read the instruction manual and follow the recommendations for cleaning pump equipment, unless given special guidelines by the NICU.

  • The pieces of the collection kit come apart for individual cleaning.

  • The pump itself and the tubing portion of the kit do not have to be cleaned, and they should remain dry or they will not work appropriately. (These pieces of equipment never come in contact with milk that is to be stored for the baby.)

  • After each use, rinse all parts that come in contact with the breast or milk in cool water first. (A cool rinse removes residual milk without coagulating hard-to-clean protein.) Then thoroughly clean these same parts in hot, soapy water. Rinse in hot water, and air dry between each use.

  • Most manufacturers recommend boiling or sterilizing all parts that come in contact with the breast or milk once a day. Sterilizing can be done in the microwave in reusable sterilization bags made by the pump company. (Check the instruction manual.)

Don't use a dishwasher to clean or sterilize the parts that come in contact with the breast or milk unless you have received permission from the NICU and the instruction manual suggests this method as a choice.

Online Medical Reviewer: Heather M Trevino BSN RNC
Online Medical Reviewer: Michele Burtner CNM
Online Medical Reviewer: Tennille Dozier RN BSN RDMS
Date Last Reviewed: 5/1/2023
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