Preventing NEC

Breastmilk is more than nutrition

Necrotizing enterocolitis is a complex condition with no single cause, test or cure. As appropriate nutrition is critical to the care of premature babies and NEC rarely occurs before a baby has been fed milk, multiple studies have looked at the links between feeding practices and the disease. Some have shown that milk from a baby’s mother, or a donor, helps to reduce the number of cases of NEC and its severity1, and current evidence2 suggests that formula is associated with a near-doubling of the risk that it will develop.

 Breast milk does not eliminate the risk, but every drop of her own milk that a mother can give her baby helps their developing immune and digestive systems. These are not just immature in premature babies, there are distinct differences compared to those of healthy babies born at term3. Breast milk helps these systems to develop in the best ways they can because it is more than nutrition: it is medicine for premature and fragile babies.

Colostrum, which is produced for a few days after birth, is a baby’s first immunisation as well as its first feed. It is rich in immunologically active cells and other protective proteins that help vulnerable babies to compensate for the time it takes them to produce their own antibodies to fight bacteria and viruses.

Colostrum collected in syringes can be given directly to babies and also fed to them through a tube. Early use of colostrum swabbing has been encouraged in some units because it helps mums to start participating in the care of their babies, but the effect of oral colostrum swabbing on NEC outcomes is not yet known.

There is not just one human milk

It is not yet understood exactly why, and how, breast milk protects against NEC in ways that formula milk does not as it contains a wide variety of bioactive compounds that often work together and in many different ways. These depend on when a baby was born and how long its mother has been producing milk (lactating).

 Human milk reflects the baby’s health:

  • it varies by gestation and age
  • its compounds change as babies grow
  • mothers of preterm babies produce higher quantities of protective proteins in their milk 
  • when the baby has an infection, mothers produce more white blood cells.

Human milk provides:

  • a mix of nutrients, helpful bacteria and antimicrobial proteins
  • the first source of immune protection in the intestines
  • conditions for helpful bacteria to grow
  • help to fight dangerous bacteria.

Early expressing helps mums start breastfeeding

While research proves conclusively that breast milk is best for babies, feeding those most at risk of NEC can be difficult for babies, their mothers and the professionals caring for them. Giving birth prematurely is often traumatic and getting breastfeeding started can be challenging. Most mothers of very preterm infants are unable to provide a sufficient volume of milk and for some first-time mothers, milk production may be limited by the immaturity of cells responsible for secreting milk. It is important that these mums are helped to express as soon after delivery as possible, ideally within an hour, when high levels of the hormone oxytocin make it easier for them to start producing milk.

Extremely premature and sick infants need to be given carefully prescribed nutrients intravenously (parenteral nutrition, PN or TPN), and they progress to enteral feeding where milk is fed into the stomach and intestines (the gastrointestinal tract). They are initially fed tiny quantities (trophic feeds), which are slowly increased, and tube-fed milk that has been expressed (pumped) and stored. The suck reflex, which babies need to be able to breastfeed, does not begin until about the 32nd week of pregnancy and is not fully developed until about 35-36 weeks.

Donor milk

Donor milk is frequently recommended as the next-best option to a mum’s own milk even though it loses some of its protective properties during the heat-treatment it receives to destroy any potentially dangerous microorganisms carried by the donor. This process is undertaken by a milk bank.

Most donors are mothers of term-born babies who are able to express extra amounts of milk, which is then collected from their homes. As the age of their babies varies, the fat, energy and protein content of the milk they donate also varies. This means that it may not ensure optimal growth for preterm or low birth weight infants, but the majority of studies of donor milk feedings either alone or in combination with mothers’ own milk have demonstrated a reduction in NEC4.

Whether the milk comes from a baby’s mum or a donor, expressing, freezing, storing, thawing and handling breastmilk does have some negative impacts on the quality of the milk and its ability to protect against NEC and other infections.

Formula milk & milk fortifiers

As premature babies can find formula more difficult to digest and there are defensive benefits to their vulnerable digestive systems that are, for the most part, missing from formula, the emphasis in neonatal units is on helping mums to breastfeed their babies. However, there are a variety of reasons why formula is sometimes needed, including the separation of mum and her baby, difficulty in meeting the needs of multiple babies and the lack of donor milk.

Formula is usually based on cow’s milk and the many different products available vary in energy, protein and mineral content. Standard formula is designed for term infants, and based on the composition of mature breast milk, while ’preterm’ formula is enriched to provide higher quantities of energy, protein and minerals. Formula is associated with faster rates of growth and higher rates of NEC, but it is not yet clear if this is due to a damaging component in infant formula or a protective element only present in breast milk5. The balance of risks and benefits of feeding formula versus donor breast milk for preterm babies continues to be debated.

In some instances, a protein supplement called fortifier is added to breast milk to provide more energy and protein for growth. It has become standard practice in many neonatal units around the world. Fortifiers use either cow’s milk (which is also referred to as bovine-based) or milk from humans, and other ingredients such as vegetable oils and corn syrup. The optimal composition of fortifiers and best fortification strategies are still objects of research and debate. Even though there is no compelling evidence that breastmilk fortifier causes NEC, many clinicians have been reluctant to use it in the past because of anecdotal evidence.


Probiotics are live organisms that are often added to yoghurts and food supplements and promoted as ‘good bacteria’. They are used in some neonatal units but this is not routine or medically regulated for premature babies. There have been trials of probiotic treatments that reported on NEC but important information has often been lacking or inconsistent and high quality, long term studies of pharmaceutical grade products given to lots of babies are needed. The value of probiotics in preventing NEC, like progress with other prevention strategies, also requires international agreement on how the condition is defined and diagnosed.

The development of therapies to prevent and treat NEC still requires many issues to be addressed. In the meantime, the best we can do to protect babies most at risk is to give them breast milk. 

Public statements

Various groups and organisations around the world have produced statements on breastfeeding and the use of donor milk. These include references to the risk of necrotizing enterocolitis. Selected paragraphs from some of these can be found by clicking on the button below:


1,5 Necrotizing enterocolitis: new insights into pathogenesis and mechanisms, Diego F. Niño, Chhinder P. Sodhi, David J. Hackam, Nature Reviews Gastroenterology and Hepatology, 18 August 2016, doi:10.1038/nrgastro.2016.119

 2 Formula versus donor breast milk for feeding preterm or low birth weight infants (Review), Quigley M,Embleton ND, McGuire W, Cochrane Database of Systematic Reviews 2018, Issue 6. Art. No.: CD002971. DOI: 10.1002/14651858.CD002971.pub4.

3 Why are preterm newborns at increased risk of infection? Collins A, Weitkamp J-H, Wynn JL. Arch Dis Child Fetal Neonatal Ed 30 January 2018. doi:10.1136/ archdischild-2017-313595

4 Human milk and necrotizing enterocolitis, Aloka L.Patel, MD,Jae H.Kim MD, PhD, Seminars in Pediatric Surgery Volume 27, Issue 1, February 2018,

Photographs reproduced by kind permission of The NEC Society.

Disclaimer: This information has been produced using contributions to meetings of the Special Interest Group in Necrotizing Enterocolitis (SIGNEC) and other research. It is intended to help parents and their families to understand this serious condition and ways in which it is treated. It is not a substitute for discussion with those responsible for the care of a baby as every baby is unique. The ultimate judgement regarding a particular clinical procedure or treatment must be made by the clinician in the light of the clinical data presented and the diagnostic or treatment options available. While all reasonable efforts have been made to check the contents of external sites, links are not an endorsement of those sites.