Human Milk Storage Information for Home Use for Full-Term Infants

Publication Date: September 1, 2017


Preparation for Human Milk Storage

Washing: Women should wash their hands with soap and water, or a waterless hand cleanser if their hands don’t appear dirty, before milk expression. Unclean hands may transmit viruses and bacteria, some of which can cause illness. Studies show that human milk containing fewer bacteria at the time of expression develops less bacterial growth during storage and has higher protein levels compared to milk that has an abundance of bacteria. Additional hand hygiene and cleaning of the breasts before expression are not necessary. (IIB)
Hand or Pump: Milk expression can be achieved by hand or by a pump. As long as the appropriate steps are taken for hand cleansing and cleaning of pump parts as per the pump manufacturer’s instructions, there does not seem to be a difference in milk contamination with pumping versus hand expression. ()


There is no need to discard the first few drops of milk with initiating milk expression. This milk is not more likely to be contaminated than milk that is subsequently expressed. One study found that milk expressed at home appears to have more bacterial contamination than milk expressed at the hospital, possibly related to equipment at home or transport, not related to personal hygiene. (IIB)
Storage Container Choice: Several studies have been done to evaluate a range of available storage containers. There is a significant reduction in percent of fat and an increase in total protein and carbohydrate concentrations with either glass or polyethylene, polypropylene, polycarbonate, or polyethersulfone bottles or bags. Glass and polypropylene containers appear similar in their effects on adherence of lipid-soluble nutrients to the container surface, the concentration of immunoglobulin A (IgA), and the numbers of viable white blood cells in the stored milk. Use of polyethylene containers was associated with a marked drop (60%) of IgA and milk’s bactericidal effect when compared to Pyrex, a type of tempered glass. Steel containers were associated with a marked decline in cell count and cell viability when compared to polyethylene and glass. (IIB)
Human milk should not be stored in hospital plastic specimen storage containers such as those used for urine or other bodily fluids because there is insufficient evidence regarding their chemical safety and effects on infants’ health. Only food grade plastic containers should be used for human milk storage. (IV)
There has been concern about possible contamination of milk stored in polypropylene bags because of the risk of contamination by puncturing the plastic. (IV)
However, one study showed no difference between contamination and fat loss when comparing hard and soft polypropylene containers. Therefore, plastic bags used for human milk storage should be sturdy, sealed well, and stored in an area of the freezer where damage to the bag would be minimized. (IIB)
Containers made with bisphenol A, which is found in several plastic containers including baby bottles, should be avoided based on strong evidence of its adverse effects as an endocrine disruptor. There should be caution about the use of bottles with bisphenol S, a bisphenol A alternative, as it may also have deleterious effects, although this is not well established in the literature.
Care of Containers: Containers for human milk storage and breast pump milk collection kits must be completely dismantled, washed in hot soapy water and rinsed or washed in a dishwasher, and should always be thoroughly air dried or dried with paper towels. They do not need to be sterilized. If soap is not available, then boiling water is preferable. (IIB)
Chemical disinfection is not ideal, as the disinfectant can be easily deactivated and could expose infant to unnecessary risk of both inadequately clean containers and residual chemical disinfectant. (IV)

Storage of Human Milk

Freshly expressed human milk may be stored safely at room temperature (10–29°C, 50–85°F) for some period of time. Studies suggest different optimal times for room temperature storage because conditions vary greatly in the cleanliness of milk expression technique and the room temperature. Warmer ambient temperatures are associated with faster growing bacterial counts in stored milk. For room temperatures ranging from 27°C to 32°C (29°C = 85°F), 4 hours may be a reasonable limit. For very clean expressed milk with very low bacterial counts, 6–8 hours at lower room temperatures may be reasonable, but it is best to chill or refrigerate as soon as possible if the milk will not be used during that time. (IIB)
Ice packs: Very few studies have evaluated milk storage safety at 15°C (59°F), which would be equivalent to an ice pack in a small cooler. Hamosh et al. suggested that human milk is safe at 15°C for 24 hours, based on minimal bacterial growth noted in the samples from their study. (IIB)
Refrigeration: Few studies have been done on the change in milk composition during refrigerator storage. One study found that lipid composition and lipase activity remained stable up to 96 hours in the refrigerator. Lactoferrin levels are stable in the refrigerator for 4–5 days. Many immunologic factors in colostrum such as IgA, cytokines, and growth factors are not diminished with refrigeration for 48 hours. (IIB)
Bioactive factors in human milk variably diminish with freezing. Lactoferrin levels and bioactivity are significantly lower in human milk frozen at - 20 C for 3 months. However, several cytokines, IgA and growth factors from colostrum are stable for at least 6 months at -20 C (-4 F). One trial evaluating milk frozen for 9 months found a progressive decline in pH and in bacterial counts, and increases in nonesterified fatty acids. Other macronutrients, osmolality, and immunoactive proteins remained unchanged in this study after 9 months. Frozen human milk should be stored in the back of the freezer to prevent intermittent rewarming due to freezer door opening, and should be kept away from the walls of self-defrosting freezers. All containers with human milk should be well sealed to prevent contamination. (IIB)
Smell of stored milk: Refrigerated and frozen human milk may have an odor different from fresh milk due to lipase-mediated triglyceride breakdown, releasing fatty acids. The odor likely comes from oxidation of these fatty acids.42,43 This lipolysis process has antimicrobial effects preventing the growth of microorganisms in thawed refrigerated milk. There is no evidence to suggest that infants often reject human milk due to this odor. Many foods that humans eat, such as eggs, cheese, and fish, have an unpleasant odor that does not affect taste. One study demonstrated that freezing human milk to -80°C (-112°F) leads to less change in smell as compared to conventional freezing to -19°C. Heating milk to above 40°C to deactivate lipase is not advised because this may destroy many of the immunologically active factors in human milk. (IIB)
Expansion while freezing: When filling a container with human milk, space should be left at the top to allow for expansion with freezing. All stored containers of human milk should be labeled with the date of milk expression and the name of the child if the milk will be used in a child-care setting. It is typical for infants in daycare to take 60–120 mL (2–4 ounces) of human milk at one feeding. Therefore, storing human milk in a variety of small increments such as 15–60 mL is a convenient way to prevent waste of thawed human milk. 7. Mixing milk: Freshly expressed warm milk should not be added to already cooled or frozen milk, to prevent rewarming of the already stored milk. It is best to cool down the newly expressed milk first before adding it to older stored milk.

Using Stored Human Milk

Cleaning of feeding devices: Containers and feeding devices used to feed the infant should be cleaned with soap and water and air dried or dried with a paper towel before/after every use. They do not need to be sterilized for a healthy infant. (IIB)
Using fresh milk first: Fresh milk is of higher quality than frozen milk. Fresh milk contains current maternal secretory IgA antibodies that may be relevant to the dyad’s recent infectious exposures. Freshly expressed milk is highest in antioxidants, vitamins, protein, fat, and probiotic bacteria compared to refrigerated or frozen milk. Fresh human milk also has the greatest immunologic activity compared to refrigerated or frozen milk. (IB)
Thawing frozen milk: There are several ways to thaw frozen human milk: by either placing the container in the refrigerator overnight, by running it under warm water, by setting it in a container of warm water or by using a waterless warmer. Slow thawing in the refrigerator causes less fat loss than thawing in warm water. (IIB)
Milk placed in hot water bath (80°C, which is not uncommon in the real setting) creates islets of high temperature milk due to lack of stirring. Overheating during the warming process causes denaturation and inactivation of milk’s bioactive proteins and decreased fat content. (IIB)
Microwaving: Studies done on defrosting human milk in a microwave demonstrate that controlling the temperature in a microwave is difficult, causing the milk to heat unevenly. Although microwaving milk decreases bacteria in the milk much like pasteurization does, it also significantly decreases the activity of immunologic factors, which may reduce its overall health properties for the infant. (IIB)
Using thawed milk: Once frozen milk is brought to room temperature, its ability to inhibit bacterial growth is lessened, especially by 24 hours after thawing. Previously frozen human milk that has been thawed for 24 hours should not be left out at room temperature for more than 2 hours. (IIB)
Refreezing: There is little information on refreezing thawed human milk. Bacterial growth and loss of antibacterial activity in thawed milk will vary depending on the technique of milk thawing, duration of the thaw, and the amount of bacteria in the milk at the time of expression. At this time no recommendations can be made on the refreezing of thawed human milk.
Using previously fed milk: Once an infant begins drinking expressed human milk, some bacterial con- tamination occurs in the milk from the infant’s mouth. The length of time the milk can be kept at room temperature once the infant has partially fed from the cup or bottle would theoretically depend on the initial bacterial load in the milk, how long the milk has been thawed, and the ambient temperature. There has been insufficient research done to provide recommendations in this regard. However, based on related evidence thus far, it seems reasonable to discard the remaining milk within 1–2 hours after the infant is finished feeding. ()
To avoid wasting or discarding unfed milk, mothers may consider storing milk in a variety of increments such as 15, 30, or 60 mL.

Handling: Expressed human milk does not require special handling (such as universal precautions), as is required for other bodily fluids such as blood. It can be stored in a workplace refrigerator where other workers store food, although it should be labeled with name and date.


Mothers may prefer to store their milk in a personal freezer pack or cooler, separate from communal refrigerator areas.

Infections: Uncontaminated human milk naturally contains nonpathogenic bacteria that are important in establishing the neonatal intestinal flora. These bacteria are probiotics—they create conditions in the intestine that are unfavorable to the growth of pathogenic organisms. If a mother has breast or nipple pain from a bacterial or yeast infection, there is no evidence that her stored expressed milk needs to be discarded. Human milk that appears stringy, foul, or purulent should, however, be discarded and not be fed to the infant. ()

Recommendation Grading




Human Milk Storage Information for Home Use for Full-Term Infants

Authoring Organization

Publication Month/Year

September 1, 2017

Supplemental Implementation Tools

Document Type


External Publication Status


Country of Publication


Document Objectives

Create guidlines for correct preparation and storage of human breast milk. 

Inclusion Criteria

Female, Adult

Health Care Settings

Ambulatory, Childcare center, Home health, Hospital, Outpatient

Intended Users

Nurse midwife, nurse, dietician nutritionist, nurse practitioner, physician, physician assistant


Counseling, Prevention

Diseases/Conditions (MeSH)

D001942 - Breast Feeding, D007224 - Infant Care, D007225 - Infant Food, D007231 - Infant, Newborn, D000068104 - Infant Health, D007223 - Infant


Breastfeeding, Breast milk storage, Human milk storage, Preparation of breast milk

Source Citation

Eglash, A., Simon, L., Brodribb, W., Reece-Stremtan, S., Noble, L., … Brent, N. (2017). ABM Clinical Protocol #8: Human Milk Storage Information for Home Use for Full-Term Infants, Revised 2017. Breastfeeding Medicine, 12(7), 390–395. doi:10.1089/bfm.2017.29047.aje


Number of Source Documents
Literature Search Start Date
January 1, 1979
Literature Search End Date
December 31, 2017
Description of External Review Process
Yes. The draft protocol is peer reviewed by individuals outside of contributing author/expert panel, including specific review for international applicability. The Protocol Committee's sub-group of international experts recommends appropriate international reviewers. The Chair and/or protocol resource person institutes and facilitates this process. Reviews are submitted to the committee Chair and resource person. The contributing author/expert panel and/or designated members of protocol committee work to amend the protocol as needed. The draft protocol is submitted to the Academy of Breastfeeding Medicine (ABM) Board for review and approval. Comments for revision will be accepted for three weeks following submission. The Chair, resource person and protocol contributor(s) amend the protocol as needed. Following all revisions, the protocol has the final review by original contributor(s) to make final suggestions and ascertain whether to maintain contributing authorship. The final protocol is submitted to the Board of Directors of ABM for approval. A two-thirds majority of Board members' positive vote is required for final approval.
Specialties Involved
Family Medicine, Obstetrics And Gynecology, Pediatrics, Preventive Medicine, Neonatology And Perinatology, Pediatrics
Description of Evidence Analysis Methods
General Methods An initial search of relevant published articles written in English in the past 30 years in the fields of medicine and basic biological science is undertaken for a particular topic. Once the articles are gathered, the papers are evaluated for scientific accuracy and significance. Specific Methods The search was conducted using PubMed. In addition, a search of the original references and literature searches (from the previous version) were used to look for additional supportive articles. The time frame for the literature search was January 1979 to December 2017. The inclusion criteria used for the searched were: humans, review articles, primary research articles, and English.
Description of Evidence Grading
Quality of evidence [levels of evidence IA, IB, IIA, IIB, III, and IV] is based on levels of evidence used for the National Guidelines Clearing House and is noted in parentheses