Human milk storage information for home use for full-term infants.
Academy of Breastfeeding Medicine Protocol Committee. ABM clinical protocol #8: human milk storage information for home use for full-term infants (original protocol March 2004; revision #1 March 2010). Breastfeed Med 2010 Jun;5(3):127-30. [35 references]
Preparation for Human Milk Storage
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 (Sosa & Barness, 1987; Pardou et al., 1994; Eteng et al., 2001).
Milk expression can be achieved by hand or by a pump. There are many factors involved in pump selection, such as cost, availability of pumps, access to electricity, anticipated frequency and ongoing duration of expression, time constraints, comfort, etc. As long as the appropriate steps are taken for hand cleansing and cleaning of pump parts as per the pump manufacturer, there does not seem to be a difference in milk contamination with pumping versus manual expression (Pittard et al., 1991; Boo et al., 2001). One study investigated fat concentration in expressed milk with manual expression versus pumping and found no difference (Garza et al., 1982).
Several studies have been done to evaluate storage containers. Glass and polypropylene containers appear similar in their effects on adherence of lipid-soluble nutrients to the container surface (Garza et al., 1982), the concentration of immunoglobulin A, and the numbers of viable white blood cells in the stored milk (Goldblum et al., 1981). Use of polyethylene containers was associated with a marked drop (60%) of immunoglobulin A (Goldblum et al., 1981). Steel containers were associated with a marked decline in cell count and cell viability when compared to polyethylene (Manohar, Williamson, & Koppikar, 1997) and to glass (Williamson & Murti, 1996). There has been concern about possible contamination of milk stored in polypropylene bags because of the risk of contamination by puncturing the plastic (Hopkinson, Garza, & Asquith, 1990). Therefore, plastic bags used for human milk storage should be sturdy, sealed well, and stored in an area where damage to the bag would be minimized. Concern has also been raised about the risk of breaking glass containers. 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 (Vom Saal & Hughes, 2005).
Containers for human milk storage do not need to be sterilized. They can be washed in hot soapy water and rinsed or washed in a dishwasher (Pittard et al., 1991). If soap is not available, then boiling water is preferable.
There is no need to discard the first few drops of milk when initiating milk expression. This milk is not more likely to be contaminated than milk that is subsequently expressed (Pittard et al., 1991).
Breasts/nipples do not need to be washed prior to expression (Pittard et al., 1991).
Storage of Human Milk
Freshly expressed human milk may be stored safely at room temperature (10 to 29°C, 50 to 85°F). Different studies suggest different optimal times for room temperature storage because the studies vary greatly in the cleanliness of milk expression technique and the room temperature during the study. 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), 3 to 4 hours may be a reasonable limit (Eteng et al., 2001; Hamosh et al., 1996; Nwankwo et al., 1988). For very clean expressed milk with very little bacteria, 6 to 8 hours at lower room temperatures may be reasonable (Pardou et al., 1994; Pittard et al., 1985; Igumbor et al., 2000; Ajusi et al., 1989).
Very few studies have evaluated milk storage safety at 15°C (59°F), which would be equivalent to a blue-ice pack in a small cooler. Hamosh et al. (1996) suggested that human milk is safe at 15°C for 24 hours, based on minimal bacterial growth noted in the samples from their study.
Several studies have demonstrated the safety of refrigerating human milk (4°C, 40°F), either by evaluating the bactericidal capacity of stored milk as a marker for milk quality or by measuring bacterial growth in the stored milk samples. Bactericidal capacity of stored refrigerated human milk declines significantly by 48 to 72 hours (Martínez-Costa et al., 2007; Silvestre et al., 2006; Ogundele, 2002). However, studies of expressed human milk with little contamination at the time of expression demonstrate safe, low levels of bacteria growth in milk at 72 hours (Igumbor et al., 2000) and even after 4 to 8 days of refrigeration (Sosa & Barness, 1987; Pardou et al., 1994; Slutzah et al., 2010).
Freezing expressed human milk (-4°C to -20°C) has been demonstrated to be safe for at least 3 months. Vitamins A, E, and B, total protein, fat, enzymes, lactose, zinc, immunoglobulins, lysozyme, and lactoferrin are generally preserved when freezing human milk (Ezz El Din et al., 2004; Friend et al., 1983; Evans et al., 1978). A few studies have found a significant decrease in vitamin C levels in frozen milk after 3 months (Buss et al., 2001; Bank et al., 1985). Bacterial growth was not found to be a problem in frozen milk for at least 6 weeks (Marín et al., 2009). Antibacterial activity of frozen human milk is preserved for at least 3 weeks (Hernandez et al., 1979). The basic principles of freezing dictate that frozen foods at -18°C (0°F) are indefinitely safe from bacterial contamination, although enzymatic processes inherent in food could persist, with possible changes in milk quality (Food Safety and Inspection Service, U.S. Department of Agriculture, 2005). Frozen human milk should be stored in the back of the freezer to prevent intermittent rewarming due to freezer door opening. All containers with human milk should be well sealed to prevent contamination.
After a container is filled with human milk, space should be left at the top of the container 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 to 120 mL (2 to 4 ounces) of human milk at one feeding. Therefore, storing human milk in 60 to 120 mL increments is a convenient way to prevent waste of defrosted/thawed human milk.
Try to avoid adding warm milk to already cooled or frozen milk, in order 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.
Stored human milk may have an altered smell and taste because of the activity of lipase, an enzyme that breaks down fat into fatty acids. This breakdown of fat aids the infant in the digestion of human milk, particularly for preterm infants, and is not harmful (Food Safety and Inspection Service, U.S. Department of Agriculture, 2005; Wardell et al., 1984), although some infants may refuse to drink it. Heating milk to above 40°C is not advised because this will result in loss of enzyme activity (Wardell et al., 1984).
Fresh milk is better than frozen milk. Use the oldest milk in the refrigerator or freezer first.
The baby may drink the milk cool, at room temperature, or warmed. Infants may demonstrate a preference.
It is best to defrost human milk either in the refrigerator overnight, by running under warm water, or setting it in a container of warm water. 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 (Ovesen et al., 1996). Although microwaving milk decreases bacteria in the milk much like pasteurization does, microwaving also significantly decreases the anti-infective quality of human milk, which may reduce its overall health properties for the infant (Quan et al., 1992; Sigman et al., 1989).
Once frozen milk is brought to room temperature, its ability to inhibit bacterial growth is lessened, especially by 24 hours after thawing (Hernandez et al., 1979). Previously frozen human milk that has been thawed for 24 hours should not be left out at room temperature for more than a few hours.
There is little information on refreezing of 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.
Once a baby begins drinking expressed human milk, some bacterial contamination occurs in the milk from the baby’s mouth. The duration of time the milk can be kept at room temperature once the baby 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 have been no studies done to provide recommendations in this regard. Based on related evidence thus far, it seems reasonable to discard the remaining milk within 1 to 2 hours after the baby is finished feeding.
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 (Centers for Disease Control and Prevention, Department of Health and Human Services, 1996). Mothers may prefer to store their milk in a personal freezer pack.
Uncontaminated human milk naturally contains nonpathogenic bacteria (Delgado et al., 2009; Heikkilä & Saris, 2003) and is 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 (Heikkilä & Saris, 2003). If a mother has breast or nipple pain from what is considered to be 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 not be fed to the baby.