The Use of Human Milk in the Neonatal Intensive Care Unit: Practices in Belgium and Luxembourg

Abstract

Background:

Human milk remains the preferred feeding for all infants, including premature and sick newborns. However, mother's milk is not sterile, and expressed milk can be a source of commensal and pathogenic microorganisms. Microbiological quality standards for the use of expressed human milk in hospitals are not available, unlike for donor or formula milk.

Methods:

To document current practices for the use of human milk in the neonatal intensive care units (NICU) in Belgium and Luxembourg, both for mother's own milk and donor milk, a questionnaire was sent to all 20 neonatal units.

Results:

Of the 19 units that completed the survey, 47% perform bacteriological testing of expressed milk. Applied bacterial count limits for the acceptable level of contamination differ among units, for both commensals and pathogens. Only six units have a device for pasteurizing milk at their disposal. Storage time in the refrigerator for fresh milk varies between 24 hours to 7 days before use. Access to donor milk is limited.

Conclusions:

Routines for handling of human milk differ widely among NICUs in Belgium and Luxembourg. An assessment of current issues through a structured survey is a useful tool in the development of best practice guidelines.

Background

The use of maternal milk in the neonatal intensive care unit (NICU) has increased, as the advantages of human milk, compared with formula, have been well established regarding enteral tolerance, host defense, and the prevention of late-onset septicemia and necrotizing enterocolitis.¹

Human milk can, however, also be a vehicle for commensal and pathogenic microorganisms derived from the mother or the environment. Numerous outbreaks and case reports of neonatal infections from contaminated milk have been described. Organisms linked to human milk-induced infections include Staphylococcus aureus, Eschericia coli, Serratia spp., Pseudomonas spp., Salmonella spp. and cytomegalovirus (CMV).^2–4

Pumping, collection, and storage of expressed human milk create opportunities for bacterial contamination and cross-infection. To ensure the safety of expressed milk, mothers should be instructed on hygienic methods for collecting milk as well as for the cleaning and disinfection of breast pumps and collection kits. Additional recommendations for transportation, storage, and handling are intended to ensure that human milk is microbiologically safe and nutritionally and immunologically complete.⁵

In contrast to formula milk,⁶ no microbiological quality standards or specific state regulations are issued for expressed human milk used exclusively for a mother's own infant in a hospital. Because of the lack of upper safe limits, the microbiological testing and pasteurization of human milk have been controversial issues across NICUs worldwide.⁷ Some NICUs choose to pasteurize mother's own milk in order to reduce risks, associated with feeding susceptible infants, to acceptable levels. Heat treatment affects some of the nutritional and immunologic components of human milk, but many immunoglobulins, enzymes, hormones, and growth factors are unchanged or minimally decreased.⁸

If mothers are unable to provide enough milk for their infants, pasteurized donated human milk is considered as the first alternative, preferred over artificial formula, especially for vulnerable infants.⁹ Pasteurized donor milk can provide many of the components and benefits of human milk without the risk of transmission of infectious agents. Although evidence supporting the use of donor milk is limited, the latest systematic reviews suggest a lower risk for necrotizing enterocolitis as opposed to formula milk.¹⁰

The aim of this study was to describe handling routines for the use of human milk in the NICUs of Belgium and Luxembourg, for both mother's own milk and donor milk, especially regarding collection, storage, and processing procedures. An assessment of current issues through a structured survey is considered to be a useful addition in order to highlight different practices and focus the questions in preparation for the development of national guidelines.

Methods

All 20 tertiary neonatal care units in Belgium and Luxembourg were contacted in February 2010 and invited to complete a questionnaire. The survey contained closed-end questions on the current practices on storage and processing of expressed milk for the mother's own infant and questions about the use of donor milk. The study was approved by the institutional review board at the University Hospitals Leuven, Leuven, Belgium.

Results were collated, and a basic analysis was undertaken. Because of the descriptive design of the study, no statistical analysis of the data was performed.

Results

Nineteen neonatal units returned completed questionnaires (a 95% response rate). All but one give written instructions regarding hygienic milk collection, transportation, and appropriate storage to lactating mothers after admission of their infant. Five units have a Baby Friendly accreditation of their associated maternity services.

Equipment for milk expression and collection

An electric breast pump is provided by the hospital (n=12 units) or hired through the hospital (n=11). The type of pump for home use can be chosen by the mother herself in most units (75%). Only one hospital does not accept milk that is collected at home. Methods used to disinfect the collection kits (shield, valve, and tubing) vary across the units: during the hospital stay of the mother, kits are either disposed of (n=12) or sent to the hospital sterile services (n=7) after each use. Rarely, patient-related kits are cleaned and disinfected by the mother in her hospital room by use of a hypochlorite solution or enzymatic cleaner. Sixteen units (85%) allow the kits to be cleaned and disinfected at home once the mother has been discharged. Neither the number of sets or containers provided for collection nor the type of container used for storage was requested on the survey.

Milk storage in the hospital

Fresh milk is kept in the hospital refrigerator for a maximum period ranging from 24, 48, or 72 hours (seven units, five units, and three units, respectively) to 7 days before use (in two units), with a median of 48 hours. In six units, excess milk is stored frozen in the hospital at −20°C for up to 3 months before use, in nine units for a maximum of 6 months, and in one unit even up to 1 year. One hospital uses only refrigerated, nonfrozen human milk, and for two NICUs the frozen milk is always stored at home. Thawed milk is mostly used within 24 hours of refrigeration, except for two units that use thawed milk for 48 or 168 hours.

Bacteriological surveillance and heat processing of mother's own milk

Nine of the 19 neonatal units (47%) routinely perform bacteriological testing of the expressed human milk. The frequency of screening of milk differs between only once before starting feeds (n=1) to weekly (n=2) or twice a week (n=2) or daily (n=2) to culturing each sample (n=1). Seven units will only screen the milk if clinically indicated: In case of feeding intolerance (n=4), in case of late-onset sepsis or necrotizing enterocolitis (n=7), or in case of maternal infection (e.g., mastitis [n=4]).

Critical bacterial count limits for the acceptable level of contamination in raw milk are applied in seven of the nine NICUs that perform microbiological surveillance. The limits vary both for commensal bacteria and for potential pathogens as shown in Table 1. Some units allow up to 10⁵ colony-forming units of skin commensals/mL in raw milk but will pasteurize the milk if counts are above this level. The presence of S. aureus in any numbers usually gives rise to discarding the milk samples. Only six units have a device to pasteurize milk at their disposal.

Table 1.

Applied Bacterial Count Limits for Mother's Own Milk in the Neonatal Intensive Care Units

	Mother's own milk
	To use fresh	To pasteurize	To discard
NICU 1	Commensals <10⁵ cfu/mL	Commensals 10⁵–10⁶ cfu/mL	Commensals or total >10⁶ cfu/mL
	Pathogens <10⁴ cfu/mL	Pathogens 10⁴–10⁵ cfu/mL	Pathogens >10⁵ cfu/mL or S. aureus, Salmonella, Shigella, Bacillus, Streptococcus present
NICU 2	CNS ≤10⁵ cfu/mL	CNS >10⁵ cfu/mL	S. aureus, Gram-negative bacilli, Bacillus >10⁴ cfu/mL
		Pathogens ≤10⁴ cfu/mL
NICU 3	Commensals ≤10⁵ cfu/mL	Commensals >10⁵ cfu/mL
		Pathogens present
NICU 4	Commensals ≤10⁵ cfu/mL	Commensals >10⁵ cfu/mL	S. aureus present
		Pathogens >10⁴ cfu/mL
NICU 5	Only colostrum	All except colostrum	S. aureus present
NICU 6	CNS ≤5×10⁴ cfu/mL	None	CNS >5×10⁴ cfu/mL
	No pathogens		Pathogens present
NICU 7	Commensals ≤10⁵ cfu/mL	None	Commensals >10⁵ cfu/mL
	No pathogens		Pathogens present

cfu, colony-forming units; CNS, coagulase-negative staphylocci.

Only one NICU routinely screens all lactating mothers for CMV, and five of the 19 units will not feed very low-birth-weight preterm infants with raw milk if the maternal CMV status is known to be positive.

Use of donor milk

Six of the 19 participating units (32%) use donor human milk as supplement to mother's own milk, especially for very low-birth-weight infants. Serological screening for potential donors is undertaken in three units, and one unit relies on the results of antenatal tests. In all six units, donated milk is heat-treated before use, mainly by Holder pasteurization (62.5°C for 30 minutes). Full traceability of the milk from individual donation to recipient is not outlined. No data about informed parental consent were collected in this survey. Nowhere did mothers receive financial reimbursement for their donation.

A preponderance of responders (68%) had never prescribed donor milk, mentioning safety and practical implications as the biggest concerns. Half of them (54%) indicated they would consider recommending donor milk for babies under their care.

Staffing and organization

Most neonatal units have a separately located milk kitchen in the unit or in the hospital where the storage and handling of maternal milk take place. There is a range of staff involved: Mostly nurses, assistant nurses, and some dieticians are in charge of the mother's own milk banks.

Discussion

Both medical professional and governmental organizations strongly recommend breastfeeding for all infants, acknowledging benefits with respect to infant nutrition, neurodevelopmental outcome, host defense, and mother–infant interaction and bonding. As such, extraordinary efforts are made internationally to encourage and support human milk feeding, including in units for neonatal intensive care.

No national guidelines exist in Belgium or Luxembourg for expressed human milk used exclusively for a mother's own infant in a hospital. This is reflected by a wide variation in practices among NICUs. Current recommendations for the use of human milk are limited to a Belgian law of 1964 stating that “the collection and storage of human milk in the NICU should occur in the best circumstances.”

Our survey shows that the process of cleaning and high-level disinfection, required for all the material that has been in contact with the milk, is not always monitored and sometimes left to the responsibility of the mother during her stay in the hospital. For equipment involved with feeding of high-risk premature infants, appropriate heating methods or single-use devices are preferable to hypochlorite solutions with risk of chemical toxicity, especially in case of inadequate rinsing.¹¹ Cost implications of disposable kits should be weighed against safety issues and workload of disinfecting the material in the hospital sterile services. As breast pumps are a potential source of contamination, guidance on the choice of correctly designed pumps with separate internal circuits and a safety valve should be provided and not be left to the choice of the lactating mother.

By implementing the principles of hazard analysis and critical control points to the daily practice of using expressed human milk, additional exogenous contamination can be prevented during the entire process of expression, collection, storage, and feeding.¹² The variety of recommended refrigerator storage time for fresh human milk, as mentioned in this survey, is based on studies showing no appreciable effect of refrigeration on bacterial growth for periods varying from 24 hours up to 8 days.^13,14 However, regular opening of the refrigerator door in the NICU and loss of nutritional integrity and bactericidal capacity of the milk should be taken into account.

Currently, pasteurization and screening of milk from the infant's biological mother are not uniformly recommended.¹⁵ No universally accepted upper limits exist for bacterial contamination of expressed human milk given to the mother's own preterm or sick infant. The criteria applied by different human milk banking organizations are for pasteurized donated milk fed to a biologically unrelated infant (Table 2). Mother's own milk should not be subjected to these stringent microbiological standards of donor milk. Based on currently available data, it is not clear what effect different microorganisms and different levels of contamination of expressed human milk have on receiving infants. Very little is known about the minimal infectious dose and how this varies in susceptible populations. In outbreaks and case reports of sepsis or necrotizing enterocolitis in NICUs linked to ingestion of contaminated human milk, clear evidence of causality is rarely based on molecular typing as proof of transmission, and further research on this correlation is required. This survey confirms that the need for additional measures for risk reduction, such as bacteriological screening or heat treatment, remains unresolved. Only half of the neonatal units regard bacteriological surveillance of expressed milk as essential prior to making a decision as to whether the milk is suitable for use in hospitalized infants; the other half finds testing of human milk only useful when it is a suspected source of neonatal sepsis or feeding intolerance. Rigorous bacterial screening would result in substantial amounts of milk being discarded, especially if no device for pasteurizing milk is available as is the case for two-thirds of the units.

Table 2.

Applied Bacterial Count Limits for Donor Milk in Milk Banks

	Donor milk
	To use fresh	To pasteurize	To discard
NICE, UK¹⁶; AIBLUD, Italy¹⁷	None	≤10⁵ cfu/mL total count and ≤10⁴ cfu/mL S. aureus and ≤10⁴ cfu/mL Enterobacteriaceae	>10⁵ cfu/mL total count or >10⁴ cfu/mL S. aureus or >10⁴ cfu/mL Enterobacteriaceae
			≥10 cfu/mL post-pasteurization
HMBANA, USA¹⁸	Commensals ≤10⁴ cfu/mL	Commensals >10⁴ cfu/mL	Any growth post-pasteurization
		Presence of pathogens
SNHBW, Sweden¹⁹	None	<10⁵ cfu/mL S. aureus and <10² cfu/mL Enterobacteriaceae and no presence of Group B Streptococcus, Salmonella, Listeria monocytogenes	≥10⁵ cfu/mL S. aureus or ≥10² cfu/mL Enterobacteriaceae or presence of Group B Streptococcus, Salmonella, L. monocytogenes
Australia²⁰	None	≤10⁵ cfu/mL total count and no presence of pathogens producing heat-stable enterotoxins, Enterobacteriaceae, enterococci	>10⁵ cfu/mL total count or presence of pathogens producing heat-stable enterotoxins, Enterobacteriaceae, enterococci
			Any growth post-pasteurization

AIBLUD, Associazone Italiana Banche del Latte Umano Donato; HMBANA, Human Milk Banking Association of North America; NICE, National Institute for Health and Clinical Excellence; SNBHW, Swedish National Board of Health and Welfare.

Postnatal acquisition of CMV through human milk seems not to be a big concern among neonatologists participating in this survey. If maternal screening during pregnancy shows CMV seropositivity, the majority of the units will still use the milk fresh, without inactivation of the virus by pasteurization.

Access to donor milk is limited in Belgium and Luxembourg. Reluctance to prescribe donor milk among neonatologists is partly due to the lack of a legal framework. The World Health Organization and UNICEF have jointly supported the establishment of human milk banking as part of international efforts to promote and support breastfeeding, but internationally the operating procedures of many human milk banks are still unregulated.²¹

Limited availability and lack of knowledge on safety issues of donor milk are identified by neonatologists as main obstacles for its use.

In conclusion, this survey shows a wide variation in routines for the use of human milk among NICUs in Belgium and Luxembourg. Because of a lack of practice guidelines, organizational standards, requirements of staff qualification, and sufficient resources, hospitals that want to promote human milk feeding in their neonatal units are committed to their own standards of self-regulation and quality control.

A representative group of neonatal staff from nine Belgian units has started a network to standardize best practice guidelines for the use of human milk provided to preterm or ill hospitalized infants. A survey, like the one presented here, can help to document the current routines before the final development and implementation of new guidelines.

Footnotes

Acknowledgments

We would like to thank all the neonatal doctors and nurses who responded to the survey and those who joined the working group for the development of national guidelines.

Disclosure Statement

No competing financial interests exist.

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