Breast milk - pumping and storing

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Pumping and storing breast milk allows you to have a supply of milk for your baby when it is needed. This can be a good option for moms who return to work after having a baby.

Keeping up a supply of breast milk can be a challenge for moms who return to work outside the home. You will need to pump and collect breast milk during the day while at the office.

Proper planning, support, and the correct equipment can help you continue to breastfeed, even after returning to work outside the home.

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Alternative Names

Milk - human; Human milk; Milk - breast; Breast pump information


Milk is made in small, sac-like glands in the breast. Hormones such as estrogen, progesterone, prolactin, and lactogen tell these sacs to grow and develop. This process starts during the second trimester of pregnancy.

The human breast does not store a large amount of milk. Your breasts will make new milk with every feeding.

Suckling causes your body to release a hormone called prolactin. This hormone tells your body to make milk. It also causes the release of oxytocin, a hormone that triggers the let-down reflex. The milk moves out of the milk gland, into the milk ducts, and into the nipple.

During every feeding, your breast milk changes.

  • At the beginning of the feeding, the milk is bluish and contains lactose and proteins, but little fat. Such milk is called foremilk.
  • The end of the feeding produces hindmilk. The hindmilk contains more fat, the main source of energy for your baby.


Before returning to work, you need to establish your milk supply and breastfeeding skills. Your baby also needs time to develop his or her breastfeeding skills.

The following help you maintain your supply of breastmilk:

  • Breastfeeding or pumping on a regular schedule
  • Drinking plenty of fluids
  • Eating healthy
  • Getting plenty of rest

Once you and your baby have a steady breastfeeding pattern, introduce your baby to bottle feeding with pumped breast milk. This allows plenty of time to establish good feeding habits. Do not start before your baby is 3 - 4 weeks old.

If you plan on using stored milk, it is best to only breastfeed when you are with your baby in the evening and on weekends.

Buy or rent a breast pump at least 2 weeks before going back to work. Start building up a supply of frozen milk.

After returning to work, you will need to pump milk 2 to 3 times a day. As the baby gets older, you may be able to reduce the frequency of pumping, and still keep up your supply.

An ideal workplace will provide a private room for breastfeeding moms, with a comfortable chair and an electric breast pump for use by all nursing mothers. If possible, arrange to nurse your baby at lunch time.

You may need to give your baby a bottle of formula if you do not get enough breaks or cannot pump a full day's worth of milk in one session. However, formula feeding lowers the baby's need for breast milk. Your milk supply will also decrease.

Every day, nurse your baby right before leaving in the morning and right when you return home from work. You may find that your baby nurses more often in the evenings on the days you work. Feed on-demand when you are with your baby.


There are a number of breast pumps on the market. Pumps may be hand-operated (manual) or work by battery or electricity. Hospital-quality pumps are available for rent through medical supply stores.

Personal models that are easy to carry are available for purchase. You should find the type that is comfortable for you to use and allows you to collect your breast milk in a reasonable period of time.

The most dependable and comfortable pumps are electric. Electric pumps create and release suction on their own and do not require much training to use.

Either a lactation consultant or the nurses at the hospital or your doctor's office can help you purchase a pump, as well as teach you how to use it. A lactation consultant is a person who specializes in breastfeeding.


When storing milk for home use, wash your hands before expressing (pumping).

  • Use 2- to 3-ounce bottles or hard plastic cups that have been washed in hot, soapy water and rinsed well. They should have a cap that fits tightly, such as a screw cap.
  • Heavy duty bags that fit into a nursery bottle are also okay. DO NOT use everyday plastic bags or formula bottle bags. They may leak.
  • Always date the milk before storing it.

Fresh breast milk can be kept at room temperature for up to 8 hours, and refrigerated for 5 to 7 days.

Frozen milk can be kept:

  • In a freezer compartment inside the refrigerator for 2 weeks
  • In a separate door refrigerator/freezer for up to 3 or 4 months
  • In a deep freezer at constant 0 degrees for 6 months.

Frozen and thawed milk can be refrigerated for up to 9 hours, but it should not be refrozen.

Never microwave breast milk -- overheating destroys valuable nutrients and "hot spots" can scald your baby. Bottles may explode if left in the microwave too long.


The two best ways to thaw frozen breast milk are:

  • By putting it in the refrigerator
  • By swirling it in a bowl of warm water

When leaving breast milk with a child care provider, make sure you label the container with your child's name and the date.

Other advice:

  • Do not refreeze breast milk once it has been thawed.
  • Do not save breast milk from a bottle that has been used.
  • Never add fresh breast milk to frozen milk.


Payne PA, Tully MR. Breastfeeding promotion. In: Ratcliffe SD, Baxley EG, Cline MK, Sakornbut EL, eds. Family Medicine Obstetrics. 3rd ed. Philadelphia, Pa: Mosby Elsevier;2008: section D.

Review Date: 
Reviewed By: 
David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc., Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Bellevue, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine.