Introduction
On our previous episode, I spoke about the multitude of benefits that maternal breast milk has for infants, especially critical infants in the NICU. I also shared what some of the common barriers are for mothers who have infants in the NICU including the common racial disparities that exist. I reviewed ways that NICU clinicians can educate, support, and encourage mothers to express milk for their infants. If you have not already, I encourage you to go back and listen to Episode 47: Breaking Down the Milk Expression and Breastfeeding Barriers Common to NICU Mothers.
For our 48th podcast episode, I review the composition of human breast milk and how the composition varies between preterm, term, and donor breast milk. I also discuss some of the anti-infective properties in human breast milk and why they are so crucial for all infants, but especially those born premature or critically ill. I discuss human milk fortification, the different formulations, and why it is so important in our preterm population. Finally, I discuss donor milk and why it is preferred over formula, especially with preterm infants, but also where it lacks in our vulnerable population. I finish out the podcast discussing why it is so crucial that we encourage all mothers to try and provide breast milk for their infants. There is a lot of important material in this podcast, but I promise that it will not be overwhelming, so get ready to get educated and empowered!
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Episode 48
The benefits of maternal breast milk
I spoke in detail on Episode 47 about many of the benefits of maternal breast milk for infants, but will give a brief summary. Studies have shown that infants fed human milk have an improvement in feeding tolerance as well as a decrease in the incidence of sepsis and necrotizing enterocolitis (NEC). The early administration of mother’s colostrum to extremely premature infants is also incredibly beneficial as it stimulates rapid growth in the intestinal mucosal lining and induces digestive enzymes.
Human milk is obviously beneficial from a nutritional aspect, but research has continued to show the presence of anti-infective properties in human milk that protect infants against infections of the gastrointestinal tract, respiratory tracts, urinary tract, and protection against ear infections, and sepsis. Also, earlier discharge from the NICU is often facilitated and Paula Meier, who is a researcher and educator in the field of human milk, stated in a 2010 article that maternal milk contains beneficial immunologic, antimicrobial, anti-inflammatory, epigenetic, growth-promoting, and gut-colonizing properties. Plus several additional studies have shown that maternal breast milk is protective against several other conditions including, but not limited to diabetes, allergic diseases, asthma, heart disease plus many more!
The Composition of Human Breast Milk
As you likely know, maternal human milk is the absolute best food for newborn nutrition that supports all of their accelerated growth in the first year. And although we understand the basic composition of human milk, every woman’s breast milk has a different complexity when it comes to the nutritional content. But, you may be wondering, what exactly is breast milk composed of?
In general, according to Boquien (2018), breast milk is made up of 87% water, 1% protein, 4% lipid, and 7% carbohydrate which includes 1-2.4% of oligosaccharides. It also contains many minerals like Calcium, Phosphorus, Magnesium, Potassium, Sodium, plus more as well as vitamins. The protein content in human milk is low and contains less when compared to cow’s milk. In fact, it is said that human breast milk contains the lowest amount of protein amongst all mammals. Human milk contains a large proportion of long-chain polyunsaturated fatty acids that are important for brain growth and development in infants. Also, compared to cow’s milk, human milk contains more cholesterol, which is a precursor of hormones and also important for brain development. Human milk also contains enzymes that allow for better lipid digestibility and more optimal utilization of triglycerides.
Maternal Breast Milk
Maternal milk, as I mentioned, contains compounds that have anti-infective properties which protect children against infectious diseases. It contains macronutrients and micronutrients. Specifically, colostrum, which is produced in the first 5 days or so after birth contains many immunity cells like macrophages and lymphocytes. Additionally, human milk’s biological components include immunoglobulins, cytokines, growth factors, hormones, antimicrobial agents, immune cells, stem cells, prebiotic oligosaccharides, and the milk’s microbiome also contains probiotic bacteria (Parker, 2021). It is these anti-infective properties that are associated with all of the health benefits for very low birthweight infants (VLBW) including a decreased incidence of necrotizing enterocolitis (NEC), late-onset sepsis, chronic lung disease (CLD), retinopathy of prematurity (ROP), and neurodevelopmental impairment.
Now that we know what breast milk does contain, what is it lacking in? Well, it has suboptimal amounts of iodine, iron, and vitamins including Vitamin D and Vitamin K – which is why it is recommended for breastfed infants or those who exclusively receive breast milk to receive supplementation of Vitamin D and why we give Vitamin K intramuscularly or as an injection at delivery to all infants to prevent severe bleeding.
Preterm Breast Milk
Now, the composition of preterm human milk is different – which I think is amazing! As women, our bodies know that we delivered a premature infant who has very important nutritional needs. Therefore, the milk of preterm mother typically contains higher amounts of protein, sodium, chloride, and magnesium when compared to term breast milk. This is a key point to remember later when we discuss donor breast milk. The protein content in the mother’s milk who delivered a preterm infant is higher when compared to term breast milk, especially during the first few days of lactation, but then it gradually declines. Additionally there are higher concentrations of certain free amino acids in preterm milk as well as secretory immunoglobulins which are important for immune protection.
Human Milk Fortification for Preterm Infants
Although preterm human milk does contain higher amounts of protein, sodium, chloride, and magnesium when compared to term milk, the levels of these nutrients remain lower than the recommendations. Therefore, human milk for premature infants is routinely supplemented with a fortifier to assist with weight gain and protein accretion.
Human milk fortifier (HMF) is a bovine milk-based fortifier that is available as either a powder or a liquid form. Additionally, there is the option of a liquid donor human milk-based fortifier which some hospitals and NICUs utilize. Donor human milk-based fortifier, though, is only available while infants are in the hospital. Both of these options are added to the mother’s expressed milk and fed to the infant. The fortifiers help to increase energy, protein, vitamins, and mineral contents to levels that are more appropriate for premature infants. It is recommended to continue fortification at least until discharge, but some infants are also discharged with a home feeding plan that includes fortification to more adequately support their overall growth. Unfortunately, the vitamin content remains suboptimal despite the use of fortification, so a multivitamin and iron supplement are often added in for the infant to receive each day.
Why is Donor Human Milk Preferred Over Formula For Preterm Infants?
As we know maternal breast milk is the best nutrition, but it is also extremely important for preterm infants to receive human milk. Specifically in VLBW infants, or those infants less than 32 weeks gestation, or infants with severe intestinal disorders, donor milk is utilized to aid in feeding tolerance due studies showing its impact on the reduction of necrotizing enterocolitis. Because of this and the additional benefits of human milk, if the mother’s milk is not fully in or if the mother is unable to or chooses not to express breast milk, the use of donor human milk is utilized over formula. Some hospitals are also able to provide the use of donor milk with term infants in the newborn nursery as well to bridge the gap until the mother’s milk is in, especially if the infant has hypoglycemia (low blood sugars), or suboptimal weight gain.
Maternal milk is almost always the preferred option, but when it is not available, donor milk is given to the infant for a certain period of time or based on the institution’s protocol. Typically it is given to infants less than 34 weeks’ gestation. It is also around 34 weeks corrected gestational age (CGA) when infants who are receiving donor breast milk (DBM) are slowly transitioned off of the donor milk over to formula. Donor breast milk may be continued longer in infants with a history of feeding intolerance, abdominal wall defects or other conditions like congenital heart disease.
What is Necrotizing Enterocolitis (NEC)?
As I previously stated, it has been well established in literature that premature infants who receive human milk have a lower incidence of necrotizing enterocolitis (NEC). Necrotizing Enterocolitis is a life-threatening disease that is more prone in preterm infants. It is an inflammatory bowel disease that mostly impacts premature infants. It is multifactorial in nature, meaning it is thought to involve or be due to several different factors. Once there is inflammation of the infant’s intestine, it leads to bacteria entering in which causes damage and/or death of the colon and intestine. Necrotizing Enterocolitis causes significant complications and may lead to death. It is a devastating disease that not only affects the infant while they are in the NICU, but it has long-term implications as well. It has been studied extensively and the research has shown that administration of human milk is associated with a reduction in NEC. Actually, the use of breast milk is considered a protective factor in premature infants and highly recommended which is why donor breast milk is used in NICUs. The mother’s milk is preferred for all of the reasons we have mentioned, but when it is not available or to help bridge the gap until the mother’s milk is in, donor breast milk is preferred over formula.
How is Donor Breast Milk Different?
But, as I alluded to previously, donor milk and maternal milk are not completely equivalent. Pooled donor milk usually includes milk from mothers who may have delivered their infant full term and are at a different stage of mammary gland maturity and lactation. Mothers who deliver preterm infants express milk that has unique, biological benefits specific for preterm infants. Since the donor human milk may have been expressed at a different stage of lactation, the composition will be varied and has been found to have less grams of protein and less fat, therefore it has a lower energy content when compared to the milk of preterm mothers. Protein, energy and fat content are all crucial for preterm growth and extremely preterm infants fed donor milk without fortification have relatively slow growth.
The sodium content in human breast milk has also been associated with impaired growth and neurodevelopment early in an infant’s life. The average sodium composition of breast milk from women who delivered their infant prematurely, or less than 33 weeks, has been reported to be 240-360 mg/L at 1-8 weeks postpartum. In a 2022 study by Perrin et al., they found low sodium concentrations amongst a geographically diverse sampling of donor breast milk from milk banks with an average of 102 mg/L, more consistent with mature breast milk (> 30 days postpartum). Therefore, infants who exclusively receive donor breast milk are likely receiving much less sodium than expected and needed. The authors indicated that even partial feedings with maternal breast milk would help to offset the risk of sodium deficiency so common with exclusive DBM feedings. If needed, infants with low serum sodium levels or suboptimal growth can be started on a NaCl supplement.
How the Pasteurization Process Impacts Donor Breast Milk
Donor breast milk must also be pasteurized to eliminate the bacterial and viral load. But, the necessary pasteurization process destroys cells, like stem cells and neutrophils. Pasteurization also negatively affects macronutrients and anti-inflammatory factors and it eliminates bacterial strains with probiotic properties. The typical commensal microbiome in maternal breast milk that is thought to help protect against neonatal complications including NEC is also eliminated through pasteurization. Also, the bioactive components of human milk, including lactoferrin and immunoglobulins are also significantly decreased.
Additionally, the freeze-thaw cycles that are utilized for storage, coupled with the prolonged storage, multiple container changes, and the processing of human donor milk affect the composition and reduce the bioactivity. Whether DBM is an exclusive diet or used in combination with the mother’s milk, pasteurized DBM is protective against NEC, but it does not confer the additional benefits known from the mother’s own milk that I mentioned at the front of the episode.
How can NICU Clinicians Support and Educate Mothers Regarding the Importance of Utilizing Maternal Breast Milk?
Despite the differences when comparing maternal breast milk and donor milk, the benefits of improved feeding tolerance and clinical outcomes support the use of donor milk for preterm infants. Therefore, as I mentioned, the use of donor human milk is highly recommended for preterm infants until the mother’s milk supply is established or as a replacement if the mother is unable to express breast milk.
But, as I mentioned in the previous episode, we as NICU clinicians need to ensure that we explain the use of DBM is meant to be used as a bridge until the mother’s milk supply is established. We want to be supportive, provide appropriate education, help minimize the barriers, and clearly support maternal lactation efforts. When donor milk is explained, it should not be an either or, but more of an adjunctive therapy until the mother’s milk supply is established. Initiation of milk expression should begin as soon as possible after delivery with the goal of no later than 6 hours after delivery.
It is vital that NICU clinicians are empathetic, share their knowledge, and try to build trusting partnerships with NICU mothers to promote their milk expression, establish breastfeeding, and nurture the feelings of motherhood. A supportive environment coupled with education, has the potential to positively impact the mother’s milk production in the NICU and beyond.
Breast Milk Sharing
Additionally, I must add that the use of non pasteurized donor milk or milk that is purchased off the internet or via milk sharing is not recommended. Donor milk that is not obtained through human milk banks has not gone through the screening or necessary pasteurization process and may expose infants to bacterial contamination, and transmission of viruses including cytomegalovirus, hepatitis and/or HIV. Donors for the human milk banks have to complete a thorough health screening, serologic blood testing, and they must follow detailed instructions on collecting, storing, and shipping milk. Luckily, the number of human milk banks are increasing.
Closing
I hope you found the review on the composition of human breast milk helpful. I think it is important for parents to know the anti-infective properties and health benefits of breast milk, especially for the preterm and high risk neonatal population. It is also amazing and paramount for parents of preterm infants to know that breast milk from a preterm mother has a different composition and is catered to the needs of a preterm infant with more protein, sodium, chloride, and magnesium.
I have no doubt that you know how beneficial human milk is nutritionally for infants, but I hope you also learned after listening how it is protective against necrotizing enterocolitis (NEC) in preterm infants. It is so imperative that parents truly know the benefits of not just human breast milk but specifically, the mother’s milk. Even if mothers do not want to put the infant to breast, if they would consider expressing milk for their infant, it is so beneficial in so many ways! So please consider it, ask questions, ask more questions, and do what you can to provide milk for your baby! As I mentioned, donor milk is available to help bridge the gap until the mother’s milk fully comes in, but it does not have the same composition and it loses a lot of its protective characteristics during the pasteurization process. And although donor breast milk is preferred over formula, especially in VLBW infants, due to its association with a reduction in NEC, maternal breast milk is always preferred.
As always, please consider sharing this episode with anyone who may gain some value from it!
References
Altobelli, E., Angeletti, P., Verrotti, A., & Petrocelli, R. (2020). The impact of human milk on necrotizing enterocolitis: A systematic review and meta-analysis. Nutrients, 12(5), https://doi.org/10.3390/nu12051322
Boquien, C. (2018). Human milk: An ideal food for nutrition of preterm newborn. Frontiers in Pediatrics, 6(295), https://doi.org/10.3389/fped.2018.00295
Brodsgaard, A., Andersen, B., & Skaaning, D. From expressing human milk to breastfeeding—An essential element in the journey to motherhood of mothers of prematurely born infants. Advances in Neonatal Care, 22(6), 560-570.
Cartagena, D., Penny, F., McGrath, J., Reyna, B., Parker, L., & McInnis, J. (2022). Differences in neonatal outcomes among premature infants exposed to mother’s own milk versus donor human milk. Advances in Neonatal Care, 22(6), 539-549.
Committee on Nutrition, Section on Breastfeeding, Committee on Fetus and Newborn (2017). Donor human milk for the high risk infant: Preparation, safety, and usage options in the United States. Pediatrics, 139(1), https://doi.org/10.1542/peds.2016-3440
Eichenwald, E. Hansen, A., Martin, C., & Stark, A. (2017). Cloherty and Stark’s Manual of Neonatal Care, Eight Edition. Wolters Kluwer.
Gardner, S., Carter, B., Enzman-Hines, M., & Niermeyer, S. (2021). Merenstein & Garner’s Handbook of Neonatal Intensive Care Nursing: An Interprofessional Approach, Ninth Edition. Elsevier.
Gomella, T., Eyal, F., & Bany-Mohammed, F. (2020). Gomella’s Neonatology: Management, Procedures, On-Call Problems, Diseases, and Drugs, 8th Edition. McGraw-Hill.
Meier, P., Engstrom, J., Patel, A., Jegier, B., Bruns, N. (2010). Improving the use of human milk during and after the NICU stay. Clinics in Perinatology, 37(1), 217 – 245.
Parker, L. (2022). Donor human milk is not the solution. Advances in Neonatal Care, 22(6), 485-486.
Perrin, M., Friend, L., & Risk, P. (2022). Fortified donor human milk frequently does not meet sodium recommendations for the preterm infant. Journal of Pediatrics, 244, https://doi.org/10.1016/j.jpeds.2022.01.029
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