Variability of Human Milk Feeds for Low Birth Weight Infants

Updated: Dec 31, 2020

Feeding low birthweight (LBW) infants was once primarily done by commercial specialty formulas. As public health emphasis on breastfeeding increased awareness and prevalence of breastfeeding, the use of human milk in the neonatal intensive care unit (NICU) became more common.

However, despite the fact that milk from mothers delivering prematurely has higher nutritional content than milk from mothers delivering at term, mainly in protein and fat, and thus calories,1 nutrient intake from human milk alone is not sufficient to satisfy the nutrition of the LBW or very low birth weight (VLBW) infants and support intrauterine growth rates.2

The American Academy of Pediatrics recommends human donor milk (HDM) as the preferred strategy for feeding preterm infants when mothers own milk (MOM) is unavailable.3 The combination of variability in MOM and the distinct difference between preterm milk and donor milk introduces complexity in calculating and delivering the proper amount of nutrients for feeding premature infants, and should be considered and controlled to ensure optimal nutrition is delivered to premature infants.

Variability of mother’s own milk (Protein, fat, and volume)

Mothers own milk varies in volume and composition over the course of lactation. Additionally, mothers delivering preterm produce milk with higher protein and higher levels of bioactive proteins when compared to mothers delivering at term.4

Commonly referenced preterm milk composition (used for blending calculations of several fortifier companies) lists protein as 1.77%.5 Review of the variability of very premature milk reveals a significantly more complex reality. The most variable composition occurs with mothers delivering very premature infants, in which case MOM can contain as much as 2.9% protein, falling to 2.3% then to 1.8% by weeks 3 and 8 respectively. In contrast, a mother delivering a full-term infant starts with an average of 2.2% protein during week 1 falling to 1.1% protein by week 8.4

Fat can also be widely variable in MOM. Blending charts commonly use 2.9% fat,5 but again, MOM from very premature infants has an average between 4% and 5%. The higher fat of mothers delivering premature infants lasts until at least 8 weeks postpartum. This varies significantly with mothers delivering preterm and at term, with the average of fat from MOM being around 3% in these populations.4

The volume produced by mothers also varies significantly depending on a multitude of factors. Pumping must commence within 6-12 hours of delivery and should be performed 8 to 12 times per day.4 Even following this exhausting schedule some mothers are unable to establish a breastmilk supply without the stimulation of a suckling infant. In this case, supplemental human donor milk is needed to deliver an appropriate volume for adequate nutrition.

Donor milk

Human donor milk can vary significantly in composition and safety depending on the source. Ethical considerations restrict collection of donor human milk until feeding of the mother’s infant has been established. Only after excess milk is available is it ethical to begin collecting milk from donors. For this reason, HDM collected by milk banks is similar in composition to later stage lactation MOM.

Even though variability of later lactation milk is less than the changes common with preterm milk, extensive variability in HDM is common. In addition to the variability intrinsic in donated milk processing technology, number of mothers commingled to form a batch, manufacturing control processes, and if the product is standardized for fat and protein all represent differences in the composition of donor milk when it reaches the hospital. In a 2020 review of donor milk conducted by Perrin et al., donor milk ranged from 0.8% and 2.2% protein and 1.1% to 7.4% fat.6 Most donor milk is commingled to form a less variable batch by blending several mothers’ milk together. This improves but does not guarantee consistency in delivery of nutrients. Even if very large batches are prepared to reducing variability of HDM, it is still significantly lower than preterm milk in protein.

How to deliver consistent nutrition in the NICU

More advanced processing techniques and technology are being utilized by Medolac to deliver standardized, safe donor milk to feed premature infants in the NICU. By standardizing with human milk cream and human milk protein, Medolac guarantees delivery of consistent composition of Benefit 18, Benefit 20, and Benefit 24. This allows hospitals to know exactly what they are adding.

Benefit 24 is the first human donor milk product standardized to mimic premature milk and allows hospitals to supplement MOM for premature infant feeding without diluting protein or calories which are essential for growth.

An example of prepared feeds is shown in the chart below:

  • Example 1 shows MOM blended with fortifier

  • Example 2 shows Benefit 24 blended with fortifier

  • Example 3 shows average donor milk blended with fortifier

Protein delivery of feeds prepared with Benefit 24 and MOM when fed at 135mL/kg/day are 3.78 and 4.05g/kg/day of protein, meeting the expert recommendations of 3.5-4.5g/kg/day protein (Koletzko 2015), while standard donor milk lags behind delivering only 3.24g/kg/day of protein at this volume.

There are many options available to nutritionists and doctors in NICUs. Optimal delivery of neonatal feed requires extensive understanding of composition and variability of the multitude of breastmilk feeds available for use in the NICU. Medolac standardized donor milk products such as Benefit-18, Benefit-20, and Benefit-24 dramatically reduce the complexity and variability currently inherent in the transition from MOM to donor breastmilk, and should be considered to simplify and optimize delivery of sufficient nutrients to infants.

Learn more about Benefit-24 donor milk nutrition with the protein of preterm milk.

Learn more about Medolac Benefit human milk-based nutrition options, Benefit-18, Benefit-20, and Benefit-24.


1. Gidrewicz, Dominica A., and Tanis R. Fenton. "A systematic review and meta-analysis of the nutrient content of preterm and term breast milk." BMC pediatrics 14.1 (2014): 216.

2. Agostoni, Carlo, et al. "Enteral nutrient supply for preterm infants: commentary from the European Society of Paediatric Gastroenterology, Hepatology and Nutrition Committee on Nutrition." Journal of pediatric gastroenterology and nutrition 50.1 (2010): 85-91.

3. American Academy of Pediatrics Committee on Nutrition, Section on Breastfeeding, Committee on Fetus and Newborn. Donor human milk for the high-risk infant: preparation, safety, and usage options in the United States. Pediatrics 2017;139(1):pii:e20163440. doi: 10.1542/peds.2016-3440

4. Underwood, Mark A. “Human Milk for the Premature Infant.” Pediatric Clinics of North America, vol. 60, no. 1, 2013, pp. 189–207., doi:10.1016/j.pcl.2012.09.008.

5. Koletsko B PB, Uauy R. Nutritional Care of Preterm Infants. Basel, Switzerland: Karger, 2014. Kim J, Chan, G, Schanler, R, Groh-Wargo, S, Bloom, B, Dimmit, R, Williams, L, Braggs G, Barrett-Reis, B. Growth and Tolerance of Preterm Infants Fed a New Extensively Hydrolyzed Liquid Human Milk Fortifier. Journal of Pediatric Gastroenterology and Nutrition 2015:665-71

6. Perrin, Maryanne T, et al. “The Nutritional Composition and Energy Content of Donor Human Milk: A Systematic Review.” Advances in Nutrition, vol. 11, no. 4, 2020, pp. 960–970., doi:10.1093/advances/nmaa014.

About the Author

Shawn Fels is the Senior Vice President of Quality and Innovation for Medolac where his team drives innovative advancements in breast milk derived neonatal nutrition products. He holds a triple degree in food science, food engineering, and industrial engineering from Oregon State University, which he completed concurrent with his career in the artisan cheese industry. His roles then progressed from artisan cheese manufacturing through quality, bioreactor management, technical services, and innovation in dairy ingredients. He found his calling with products designed to improve neonatal outcomes when he moved to work with Medolac full time in 2017.