Necrotizing enterocolitis (NEC)

What is necrotizing enterocolitis?

Necrotizing enterocolitis, or NEC, is a gut disease and a common cause of death in very premature babies. NEC occurs when the wall of the intestine is injured and starts to die. There may be abnormal breathing, a slow heart rate, a bloated tummy, or blood in the stool. In later stages, there may be leaking of the gut contents into the tummy, causing infection. NEC is more common in babies who receive cow’s milk-based infant formula whereas a mother’s own milk and human donor milk helps protect the gut of premature babies.

A) Describing necrotizing enterocolitis

1) Explaining necrotizing enterocolitis

The term necrotizing enterocolitis, or NEC, can be broken down:

  • Necrotizing refers to death or damage.
  • The prefix entero- means bowel-related.
  • Colitis is inflammation of the lower bowel (colon).

NEC is a severe gut disease that can develop in babies within weeks of birth. It occurs when the wall of the intestine is injured and starts to die.

NEC is a common cause of long-term disability and death in premature babies (Jones 2020). It is estimated that about one in five babies with NEC will die and about one in three of those requiring surgery will do so. Developmental disability is estimated in one in four to one in two babies.

Please discuss any concerns about NEC with your health-care providers.

2) Problems caused by necrotizing enterocolitis

NEC can cause lifelong problems, including:

  • Bowel narrowing or blockages
  • Poor bowel function (difficulty absorbing nutrients [short-bowel syndrome] such as iron [anemia])
  • Slow growth
  • Delayed brain development (Hansen 2019; Lapidaire 2021; Matei 2019)
  • Cerebral palsy (Matei 2019)

B) Signs of necrotizing enterocolitis

NEC has various stages with different symptoms (Lee 2003). These can include:

  • A bloated, painful tummy
  • An inability to empty the stomach
  • Blood in the stool
  • Bowels that do not work
  • Leaking of the bowel
  • Periods of not breathing or slow heart rate
  • Abnormal blood tests (blood too acidic, too few clotting cells)

C) Causes of necrotizing enterocolitis

NEC is more likely to develop in babies who (Isani 2018):

  • Are born small.
  • Experience decreased blood flow or low oxygen levels.
  • Have less healthy gut bacteria (microbiome).
  • Receive infant formula.

NEC can start once a baby begins to take in milk. The gut of a premature baby is different from that of a full-term baby in many ways. It:

  • Is less able to move contents along.
  • Has a weaker protective coating on the gut lining.
  • Is more likely to leak.
  • Has an immune system that can damage itself by overreacting to challenges.
  • Has difficulty providing the right amount of blood to different parts.

D) Treating necrotizing enterocolitis

The treatment of NEC can include:

  • Monitoring the baby by:
    • Testing blood for infection and chemical imbalances.
    • X-rays of the tummy.
    • Watching the size of the baby’s tummy.
  • Stopping all feeding by mouth and instead giving nutrients into a vein (TPN).
  • Placing a tube into the baby’s stomach to suction air and fluid.
  • Antibiotics.
  • Providing the baby with extra oxygen.
  • Using a machine to help the baby breathe.
  • Giving the baby blood or platelets.
  • Surgery to remove damaged parts of the bowel or create a temporary opening on the tummy (ostomy) to allow the bowel to rest and heal.

E) Preventing necrotizing enterocolitis

The research concerning the prevention of NEC is continuing. 

1) Using human milk

The rate of NEC is much lower when babies are fed the mother’s own milk instead of infant formula. The exact mechanism for this is not known. Mother’s own milk has many bioactive agents, such as helpful bacteria, that work together to protect and mature the baby’s gut (Nolan et al. 2019). Mothers own milk can:

  • Protect from infection.
  • Promote antioxidant action.
  • Promote growth.
  • Promote healthy gut bacteria.
  • Prevent leaking out of the gut.
  • Prevent inflammation (Panczuk 2016).

Pasteurized donor human milk (DHM) has less of these but is still far superior to infant formula (Yang 2020). Premature babies who receive regular infant formula instead of DHM are nearly twice as likely to develop NEC (Quigley 2018).

Infant formula made of broken-down cow’s milk protein (hydrolyzed) does not appear to offer any benefits over regular infant formula in the prevention of NEC or in decreasing feeding problems (Ng et al. 2019).

2) Milk fortifier

Very small premature babies have extra nutritional requirements that human milk cannot always meet. To compensate, health-care providers sometimes add fortifier to breast milk. Fortifier provides nutrients such as protein, calcium, and phosphorous.

Until recently, fortifier has been made out of cow’s milk. There are now two new types of fortifier; one made from human milk and the second from broken-down (hydrolyzed) cow’s milk. It is possible the former prevents NEC or offers other benefits but there is currently limited research. The latter does not appear to offer any benefits over regular fortifier in the prevention of NEC or in decreasing feeding problems (Arslanoglu 2019). 

3) Other ways of preventing NEC 

Antibiotics and medications that suppress the production of stomach acid appear to increase the risk of NEC (Gephart 2017).

Probiotics are often given to prevent NEC. 


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Lapidaire W, Lucas A, Clayden JD, et al. Human milk feeding and cognitive outcome in preterm infants: the role of infection and NEC reduction. Pediatr Res. 2021 Jun 24 

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