Which milk / When to start / How much to give to preterm babies
You are the Neonatal Registrar on call, and you admit a preterm baby born at 29 weeks GA to the NICU.
The nurse asks you about the feeding plan.
To grow and develop normally, babies need their nutritional requirements for carbohydrates, fat, protein, vitamins, and minerals met. Infants born prematurely and/or of very low birth weight will need extra calories compared to their term counterparts.
Energy supply must meet resting energy expenditure (REE), plus the requirements of any physical activity, diet-induced thermogenesis, and, importantly for preterm infants, tissue deposition (growth).
The ideal 17-20g/kg/day weight gain can be achieved via Mother’s Own Milk (MOM), donor human milk or preterm formula. But which one to choose? And most importantly, is it your choice as the doctor, or is it the parents’ choice?
Which milk is the best?
Option 1: Mother’s Own Milk (MOM)
Mother’s own milk has been proven time and again to be the best option, as it confers benefits in both the short and long term and improves bonding. Let’s also not forget the positive psychological impact on mothers when able to feed their babies with their own milk and what this does to their sense of self-worth during one of the most vulnerable times of their lives.
We all know and need to emphasise to parents that MOM provides nutrition and immune protection against infections, late-onset sepsis, NEC, BPD, and ROP; reduces re-hospitalisations in the first year of life; and leads to better neurodevelopmental outcomes.
In addition, premature infants who receive human milk carry these benefits into adolescence, with lower rates of metabolic syndrome, lower blood pressure, and less insulin resistance than those receiving formula.
Among these benefits, perhaps the most compelling is the observed decrease in NEC, a disease that carries significant morbidity and mortality. The protective mechanisms are likely multifactorial and include immunoglobulins, growth factors, digestive enzymes and pre- and probiotics present in human milk. Human milk feeding also appears to have a dose-response effect. For instance, a dose of mother’s own milk > 50 ml/kg/d may decrease the risk of late-onset sepsis and NEC compared to < 50 ml/kg/d, and for each 10 ml/kg/d increase in human milk in the diet, there is a 5% reduction in hospital readmission rate.
Did you also know that there is a difference between milk from women who deliver prematurely compared to that of women who deliver at term? Preterm milk initially has higher levels of protein, fat, free amino acids, and sodium, but these levels decrease in the first few weeks. The mineral content (including trace minerals) is similar, with the exception of calcium, which is significantly lower in preterm milk than term milk and does not appear to increase over time, while copper and zinc content are both higher in preterm milk than term milk and decrease over the time of lactation.
Option 2: Donor expressed breast milk (DEBM)
If mother’s own milk is unavailable or insufficient, DEBM is the next-best option. This will need to be discussed with the parents, and a written consent form will likely be required before starting. Most parents will, understandably, have many questions: where is it coming from? Has it been tested? What are the risks, and for how long can baby have it? So, it is a good idea to anticipate these questions and provide a confident and clear answer.
DEBM comes from a certified milk bank where milk is pasteurised to prevent transmissible infections, and mothers have had extensive health screening, including serology testing for HIV, Hepatitis B and C, syphilis and HTLV, prior to donating. Strict regulations govern who can donate and how donor milk is handled to prevent infections. However, DEBM has lower nutritional value because its fat content is less easily absorbed (due to denaturation of the bile salt-stimulated lipase enzyme through pasteurisation) and its biological activity is reduced (heat reduces anti-infective agents). Still, it has been proven to be superior to preterm formula.
DEBM is used as a short-term intervention while mother’s supply builds up to sufficient volumes or to bridge these vulnerable infants until they can safely start formula. It is offered only to a select few infants who meet the criteria, and every unit should have guidelines for its use.
A note on fortification
Often, mother’s own milk and DEBM are not nutritionally sufficient for the needs of a preterm baby, or the baby cannot tolerate large volumes of feeds. In this case, fortifiers are used to boost milk’s nutritional value and achieve optimal growth.
However, its use is not without risk. Fortification of human milk increases its osmolality, and high osmolality is associated with an increased risk of NEC. Handling fortifier powder also increases the risk of bacterial contamination and metabolic acidosis.
Option 3: Preterm Formula
Several special preterm formulas provide higher protein and mineral content than term formula and were developed in line with ESPGHAN guidelines. Examples: SMA Gold Prem 1; Aptamil Preterm; and Cow and Gate Nutripem 1 are commonly used in the NICU. Aptamil Preterm and Cow and Gate Nutripem 1 are also halal certified.
Do not give soy-based formulas to preterm infants.
Other special milks like the ones used for infants with malabsorption, inborn errors of metabolism or allergy have not been created to meet the preterm nutritional requirements, so extra monitoring and adaptations may need to be done.
When to start and how much to give?
Give colostrum as soon as it is available, in the order it is expressed. Start minimal enteral feeding (trophic feeding) with 0.5-1 mL every 4 hours, as it encourages gut motility and secretion of gut hormones. An umbilical artery catheter (UAC) should not be a contraindication to starting feeds if you follow precautions.
In babies at high risk of NEC, increase volume slowly to 20 mL/kg/day and monitor gastric residuals to avoid milk pooling in the stomach. For babies at lower risk of NEC, you can increase milk volume slightly faster.
The preferred method is via an orogastric or nasogastric Tube. Check the tube position before use, and perform regular aspirations.
Even intubated babies can benefit from their mother’s own milk. It can be used for mouth care and help establish the gut microbiome[SK3].
Sustained nipple feeding is rarely possible in babies less than 34 weeks, but putting a baby less mature to the breast would significantly improve mother’s morale, her milk supply and bonding. Non-nutritive sucking (mother pumps first and then places the baby to the breast) can be attempted as soon as the baby is extubated and stable, with success noted as early as 28 weeks corrected gestational age. Assistance from an experienced nurse or infant feeding specialist is invaluable.
When to stop feeds?
- Consistent aspirates of >50% feed volume
- Aspirate is bloody or bile-stained
- Signs of intestinal obstruction
- 4-6 hours post extubation
- During exchange transfusions
- Feeding that triggers apnoeic attacks
- Suspicion of inborn errors of metabolism
What if the mother takes medications?
There are only a few medicines that would make the breast milk unsafe, and these are: chemotherapy and immunosuppressant drugs, radioactive medicines, lithium, amiodarone, gold salts, oral retinoids like isotretinoin, illegal substances, among others.
If you are unsure, please check with your local pharmacist.
Improving breastfeeding rates for premature infants
Premature labour and delivery are highly stressful to parents. Emphasise education on the importance and value of expressing breast milk when premature delivery seems likely, and throughout admission.
Teach mothers how and when to express, and encourage them to continue even if volumes are low at the beginning. Interventions to increase production include increased skin-to-skin time, stress reduction, careful attention to diet, sleep, and pumping schedule, and medications. Domperidone can increase milk production.
Colostrum and EBM are referred to as ‘liquid gold’, and we, as doctors, also have a significant role in promoting and educating parents regarding its benefits.
The Bottom line
Human milk, especially mother’s own milk, is the best option for feeding a preterm baby due to its nutritional contents, its biologically active properties, and psychological impact for both short- and long-term development and disease prevention.
It’s everyone’s responsibility to educate parents and encourage breast milk expression for a successful breastfeeding journey.
Human milk can be started as soon as it is available.
References:
Rennie, J.M. and Kendall, G.S. eds., 2025. A manual of neonatal intensive care. CRC Press.
Embleton, N.D., Jennifer Moltu, S., Lapillonne, A., Van Den Akker, C.H., Carnielli, V., Fusch, C., Gerasimidis, K., Van Goudoever, J.B., Haiden, N., Iacobelli, S. and Johnson, M.J., 2023. Enteral Nutrition in Preterm Infants (2022) A Position Paper From the ESPGHAN Committee on Nutrition and Invited Experts. Journal of Pediatric Gastroenterology and Nutrition, 76(2), pp.248-268.
Moro, G.E. and Arslanoglu, S., 2020. human milk in the feeding of preterm infants: established and debated aspects. Frontiers in Pediatrics, 8, p.378.
Joosten, K. and Vermeulen, M., 2024. Principles of feeding the preterm infant. Clinical Nutrition ESPEN, 59, pp.320-327.
Underwood, M.A., 2012. Human milk for the premature infant. Pediatric Clinics of North America, 60(1), p.189.
