Donor human milk (DHM) has rapidly become the second best choice for feeding very low birthweight (VLBW; <1500 grams birthweight) infants during NICU hospitalization when mothers’ own milk (MOM) is not available. In this practice change from formula to DHM, many of the superior health and cost outcomes of MOM feedings have been generalized to DHM, despite the lack of evidence to do so. In fact, the two types of milk are often combined into a common “human milk feeding” metric for both research and clinical quality improvement initiatives, with little or no information about the relative proportions of DHM and MOM received by the infant.
A recent publication in the Journal of Pediatrics has targeted the differences in health outcomes and costs for DHM and MOM. A primary conclusion is that NICUs invest precious resources into the acquisition of DHM that might otherwise be directed toward the prioritization of MOM feedings, including access to evidence-based, NICU-specific lactation care and equipment such as effective breast pumps and adequate numbers of freezers and refrigerators for on-site storage of MOM.
Multiple studies have demonstrated that MOM feedings reduce the risk, incidence and/or severity of necrotizing enterocolitis (NEC), late onset sepsis (sepsis), bronchopulmonary dysplasia (BPD), retinopathy of prematurity (ROP), neurodevelopmental problems, and rehospitalization when compared to formula feedings. Furthermore, studies have detailed the NICU cost savings associated with a reduction in NEC, sepsis, and BPD that is attributable to MOM.
In contrast, a recent Cochrane review demonstrated that only NEC is reduced by substituting DHM for formula, and that DHM has no impact on other NICU morbidities. The reduction in NEC is clinically significant and is an evidence-based indication for the use of DHM rather than formula during the critical early post-birth exposure period when the risk of NEC is the greatest. However, it is likely that DHM reduces NEC because DHM does not contain bovine-based protein which separately increases gut epithelial cell cytosis, intestinal permeability, and local and systemic inflammation.
This knowledge has allowed NICU care providers to introduce early enteral feedings of DHM when MOM may be unavailable immediately post-birth, thus decreasing the inflammation associated with prolonged TPN and NPO status. However, there remains concern that VLBW infants do not grow adequately on DHM unless it is “super-fortified” with exogenous bovine protein, raising the question as to whether exposure to the bovine-enriched DHM is clinically different from exposure to formula, especially after the highest risk of NEC has passed.
Although previous reviews of DHM have focused on the role of pasteurization with respect to differences in composition for DHM and MOM, the Journal of Pediatrics review highlights additional mechanisms that impact these differences in clinically significant ways, demonstrating that even improvements in pasteurization technologies will not remedy differences in DHM and MOM. These additional differences include: mammary gland maturity (e.g., preterm versus term milk); stage of lactation (e.g., colostrum and transitional milk versus mature milk); multiple temperature changes (e.g., pasteurization and freeze-thaw cycles); impact of digestive processes and the use of bovine-based fortifiers that have not been separately tested with DHM.
For several MOM components, the effect of these multiple processes is cumulative, and is best illustrated by lactoferrin, a potent anti-infective, anti-inflammatory cytokine that has multiple protective roles including neuroprotection. Lactoferrin is the highest in the first 5 days of colostrum, declines steadily through 2 months of lactation to approximately 1/3 of its colostrum value, is further reduced up to 50% and 88%, respectively, with freezing and pasteurization, and is further inactivated by iron in bovine fortifiers. Thus, little functional lactoferrin remains by the time that DHM is received by VLBW infants in the NICU.
Also misunderstood by many clinicians is the fact that absolute amounts of MOM components may be unchanged in DHM, but their nutritional and bioactive impact is diminished. An excellent illustration of this concept is MOM lipid for which the absolute content may be unaltered in DHM but the combined freeze-thaw cycles and the eradication of lipase with pasteurization impact the digestion and absorption of DHM lipids. Separately, some bioactive MOM-borne components are optimized or activated only when fed to the infant due to the interaction of these components with each other and/or with endogenous infant pathways and receptors. Thus, the lack of absolute differences in the amount of DHM and MOM components does not assure that the mechanisms necessary for bioactivity have been preserved.
The most clinically significant difference between DHM and MOM is the lack of fit when DHM replaces MOM during the first 14-28 days post-birth. During this time, the gut of the VLBW infant is dependent upon MOM components for protection, growth, maturation and colonization. These processes are essential to reduction in the risk of NICU morbidities. MOM feedings during this critical window are the most protective due to stage of lactation and the immature mammary gland, and appear to mirror the biology of the recipient infant. These marked differences are detailed in a table in the Journal of Pediatrics publication.
DHM has an important role in the reduction in NEC for VLBW infants when it replaces infant formula during the introduction and advancement of enteral feedings. However, only MOM–not formula or DHM–protects from multiple other morbidities during and after the NICU hospitalization in a dose-response relationship with higher doses of MOM providing the greatest reduction in risk of morbidities.
This evidence raises the question as to how to prioritize resources in the NICU: toward acquisition of MOM or DHM? Multiple studies have outlined best NICU practices for the acquisition of MOM including: breast pump use within the first hour post-birth; use of hospital-grade electric breast pumps that are effective, efficient, comfortable and convenient as demonstrated by randomized studies; avoidance of hand-expression only practices (e.g., those which emphasize not using a breast pump) in the first days after birth; proactive daily monitoring of lactation processes during the first two weeks post-birth; use of NICU-based breastfeeding peer counselors, and access to NICU lactation experts with skill in breast pump dependency and lactation technologies.
All too often, NICU care providers lament that they were aware of this evidence but cannot implement the resultant practices due to the costs involved in personnel, training and lack of third party payments. The default is investing in a DHM infrastructure which is more costly and provides a second-best diet for recipient infants, but is more easily “sold” to institutional decision makers as a necessary part of NICU care. The blurring of outcomes with respect to DHM and MOM have made these resource allocations more acceptable for all, so it is time to carefully examine the evidence and invest precious dollars into prioritizing the acquisition of MOM for VLBW infants.
View the full, recorded webinar of Paula’s presentation,
Meier PP, Esquerra-Zwiers A, Patel AL. Donor human milk update: Evidence, mechanisms and implications for research and practice. (2016). e-pub ahead of print. Journal of Pediatrics.