Importance of Breast Milk for Preterm Babies

By Krista Gray, IBCLC. Last updated February 5, 2013.

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We’ve all heard the expression “breast is best,” and it is, but when it comes to preterm babies, breastmilk is not just best; it is medicine.  The time to decide whether or not to breastfeed a premature baby is not when you give birth early.

The most important thing you can do at this time is express your milk; once your baby reaches full term you can make the decision whether or not to carry on breastfeeding.

Preterm babies have unique nutritional needs, and preterm breastmilk is also unique and different to breastmilk of mothers birthing full term babies.  Preterm milk is packed with nutrition, containing higher concentrations of fat, energy, protein, calcium, potassium, magnesium, sodium, chloride, and iron.

The milk becomes more like the milk of a mom with a full term baby about three weeks later.1

Preterm babies need increased amounts of protein and energy.  The protein in breastmilk is primarily whey, which is easier to digest than protein in artificial formula. And, it takes greater energy to digest artificial milk than breastmilk.2

That said, the “fortification” of breast milk for preterm babies is very commonly encouraged by doctors.  The reasoning is that fortification allows the baby to still receive breast milk but also increase the caloric content so that the baby can put on weight more quickly.

However, research shows no weight differences in preemies who received fortified breast milk vs. those who received breast milk alone by 12 months of age.3

Birth weight does matter, though, when it comes to nutritional needs of preterm babies.  Though any baby born before 37 weeks is considered preterm, size can vary widely depending on how early a baby is born.  A low birth weight baby weighs less than 2.5 kg; a very low birth weight baby weighs less than 1.5 kg; and an extremely low birth weight baby weighs less than 1 kg.

A low birth weight baby can meet all her nutritional needs from mother’s milk alone.  Protein needs of very low birth weight infants are high and the protein in mother’s milk can vary. . . starting out higher in preterm milk and gradually decreasing.

Therefore, the current recommendation is to individualize protein supplementation (milk fortification) based on the size of the baby and the protein content of the mother’s milk.4

One way to increase weight gain of a preterm baby on unfortified breastmilk is to use the breastmilk at the end of expressing which has a higher fat content.  Typically, moms who express for their premature babies have an abundance of breastmilk as they are trying to build a solid supply for when their baby is able to nurse efficiently at the breast.

Preemies typically can’t take in this much milk so there is additional milk.  Using the milk from the end of a pumping session, as well as milk pumped in the evenings will typically yield higher fat contents. 5

Though sometimes is it is necessary to fortify the milk of very low and extremely low birth weight babies, there are still risks.  Numerous studies document a greater susceptibility to infection as well as a risk of contamination in preparing formula, greater incidence of gastrointestinal diseases, increased risk of allergies and diabetes, and the neutralization of many of the anti-infective properties of breastmilk.  When even a small amount of formula can keep a baby’s body from being able to absorb many of the nutrients in breastmilk.

While breastmilk alone is healthiest and fortified breastmilk poses some risks which must be weighed against the baby’s need for additional calories/nutrition, formula feeding has many detrimental effects on the preterm baby.

When comparing infection rates of babies given breastmilk vs. formula, the results are staggering.  Formula-fed babies have significantly increased rates of urinary tract infections, septicemia, diarrhea, necrotizing enterocolitis, and need for antibiotics. 6

If you have a preterm baby, the very best thing you can do is give your baby your breastmilk – whether this is at the breast or through expression.  More than just nutrition, it is filled with digestive enzymes, anti-bacterial and anti-inflammatory properties, growth factors, and protective factors specific to your preterm baby.  It could be a matter between life and death.  If you doctor wants to fortify or supplement your milk, make sure you understand the pros and cons and have all the information for your specific situation.  Many times, especially in the case of low birth weight babies, your breastmilk is completely adequate to help him grow and thrive.  It can be hard to go against the recommendation of the medical establishment, but if you are uncomfortable with the recommendations of your neonatologist, involve a lactation consultant and see if there is a compromise that can be worked out that you are both comfortable with.  Finally, realize that you have those “maternal instincts” for a reason and, many times, they are exactly what your baby needs.

Show 6 footnotes

  1. Paul VK, Singh M, et al. (1997) Macronutrient and energy content of breast milk of mothers delivering prematurely Indian Journal of Pediatrics 64(3):279-82
  2. Lubetzky R, Vaisman N, Mimouni FB, Dollberg S. (2003) Energy expenditure in human milk- versus formula-fed preterm infants Journal of Pediatrics 143(6):750-3
  3. Kuschel CA, Harding JE. (2004) Multicomponent fortified human milk for promoting growth in preterm infants. Cochrane Database System Review.
  4. Arslanoglu S, Moro GE, Ziegler EE, . (2010) Optimization of human milk fortification for preterm infants: new concepts and recommendations. Journal of Perinatal Medicine. 38(3):233-8
  5. Lubetzky R, Littner Y, Mimouni FB, Dollberg S, Mandel D. (2006) Circadian variations in fat content of expressed breast milk from mothers of preterm infants. Journal of the American College of Nutrition. 25(2):151-4
  6. Schanler RJ. (2001) The use of human milk for premature infants Pediatric Clinics of North America 48(1):207-19
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