Donor breast milk banking
Authors: Neena Modi
Journal: BMJ (2006)

Mother's milk is recommended for all babies, but mothers of preterm babies and other babies in intensive care are often unable or too ill to provide enough milk for their baby's needs. Mother's milk protects against infection and enhances neurocognitive development; it may also improve enteral tolerance and long term metabolic health as well as reduce asthma and other atopic disorders. Donor breast milk from a human milk bank and formula are options to make up the shortfall. The extent to which pasteurised donor breast milk retains the biological properties of mother's milk is uncertain, and its place in present day neonatal intensive care is unclear. 

Donor human milk is not the optimal food for preterm growth.1 This is especially a problem because preterm infants also have limited tolerance for large volumes of milk and because infants who receive milk by gavage or spoon, unlike those who suckle at the breast, cannot regulate energy intake.2 The protein and mineral content of donor milk can be increased by breast milk fortifier or formula, but this is an imprecise science as the composition of human milk is very variable. Composition alters with maternal diet; the energy content of milk is lower at the beginning of a feed than at the end and in drip breast milk than in expressed breast milk. Donors have also usually delivered at term or have been lactating for some time, both of which result in lower nutritional content. Milk banks in the United Kingdom do not determine the nutritional content of donor breast milk. For these and other reasons it can be difficult to achieve an adequate nutritional intake in preterm infants.3

Human milk can transmit infection. HIV is the most well recognised viral pathogen, but transmission of cytomegalovirus is not uncommon, and raw breast milk can cause serious and even fatal illness in preterm babies.4 Pasteurisation (62.5°C for 30 minutes) is necessary but this destroys or reduces many of the unique biological properties for which human milk is valued. 

In contrast to blood banks, which are tightly regulated, human milk banks in the UK vary in size and operating procedures and are unregulated, except for the voluntary adoption of standards of practice laid down by the UK Association of Milk Banks (www.ukamb.org). In Canada, Mexico, and the United States the Human Milk Banking Association of North America (www.hmbana.org) has different standards. For example, in the US milk donations are not accepted from women who were in the UK for more than three months, or in Europe for more than five years, between 1980 and 1996, presumably because of the dangers of Creutzfeldt-Jakob disease. In the UK, unlike the rest of the world, donor breast milk is not pooled, but is prepared in aliquots from individual donors. 

What evidence is there to support the use of donor breast milk? A meta-analysis of trials in preterm newborns, all conducted in the early 1980s, showed that donor breast milk reduced the risk of necrotising enterocolitis—a serious inflammatory condition of the bowel—when compared with formula.5 Infant growth was slower, however, and benefit was seen only when breast milk or formula was the sole source of nutrition. Current practice aims to use donor milk as a supplement to mother's milk and not as sole diet. Only two studies have compared outcomes when either donor milk or formula was used as a supplement to mother's milk.6 7 Neither found a significant difference in the rate of necrotising enterocolitis. For other less frequent indications, and for long term outcomes, justification for using donor milk is anecdotal. Thus, the role of donor breast milk in current neonatal practice remains to be established. 

Where does this leave us? Human milk banks around the world have arisen through the voluntary efforts of committed individuals. Their altruism is undeniable, but unregulated expansion of human milk banking requires evidence of benefit. Donor breast milk is expensive, and although donors are unpaid the cost of UK human milk banking (£30-150 per litre) is probably an underestimate of the full cost to the National Health Service.8

These uncertainties are reflected in the divergent attitudes of clinicians towards the use of donor milk and compounded by variations in acceptability by different communities.9 Research is needed in four key areas: to determine whether donor milk, when used as a supplement to mother's milk, has short term or long term benefits (or both) for preterm and growth restricted newborns, who are at particular risk of necrotising enterocolitis and adverse neurodevelopmental outcome, and for other groups such as babies who have undergone surgery, who are at high risk of milk intolerance; to conduct an economic assessment of the cost of human milk banking to the NHS; to evaluate counselling and practical support to enhance successful lactation in mothers who deliver preterm10; and to explore cultural and social attitudes to donor breast milk. 

The UK has 17 human milk banks and some 255 neonatal units. If donor breast milk is beneficial, clinical guidelines should reflect objective evidence, access should be equitable, and milk banking procedures should be consistent. If it is not beneficial NHS resources might be better directed towards supporting mothers' own lactation.