What Is Necrotic Enterocolitis (NEC)?- Information For Parents

preemie with NEC in NICU

Necrotic Enterocolitis or NEC is a severe abdominal condition affecting mostly extremely premature babies and micro-preemies. It usually occurs two weeks or later after birth and may result in long-lasting adverse consequences for the baby or even death. 

After a tiny baby overcomes initial acute respiratory distress after birth, diseases such as NEC, BPD, ROP, and infections may affect negatively well being of very premature babies. After two weeks of age, of the four conditions mentioned, NEC and infections are the most likely to be the cause of death in babies during their NICU stay. 

The main focus of this article is to provide useful information about NEC to parents and families of newborn babies hospitalized in the NICU. My article will not replace conversations that you need to have with doctors and nurses treating your baby, but hopefully, it will help you understand this complicated topic better. 

Definition of NEC and Background information


Necrotizing Enterocolitis or NEC is a severe condition affecting the gastrointestinal tract in a newborn baby. The actual mechanism and etiology of the disease are poorly understood, but we believe that several processes play a role in its development:

  • decreased blood flow to the bowel loops
  • necrosis (death) of the intestinal lining (=intestinal mucosa)
  • inflammation in the intestines
  • microorganisms entering into intestinal lining and sometimes into the blood vessels
  • the gas produced by microorganisms is entering intestinal walls and blood vessels
  • sometimes previously mentioned processes lead to rupture of the bowel loops’ walls and a severe infection in the abdominal cavity called peritonitis


90% of NEC cases occur in premature babies and only about 10% in full-term babies. The incidence of NEC in babies born at less than 32 weeks of gestational age varies from 2% to 7%. The frequency of the disease increases with decreasing gestational age at birth and lower birth weight. Micro-preemies are the most affected group of babies (Source).

Table 1: Incidence of NEC and Gestational Age; adapted from the source cited above. Incidence rates include all types of NEC (stage 1-3).

Gestational Age at BirthIncidence of NEC
Less than 26 weeks14%
26-28 weeks10.8%
28-32 weeks3%

Table 2: Incidence of NEC and Birth Weight; adapted from Kastenberg’s study

Birth WeightIncidence of NEC in the NICU
Less than 1000 grams9.4%
1000-1499 grams3.9%

Necrotic Enterocolitis in Term Babies

Up to 10%-15% of NEC cases are found among full-term babies. Usually, those babies will have additional factors that put them at higher risk for this condition:

  • severe congenital heart abnormality
  • gastrointestinal anomalies
  • small birth weight for gestational age (IUGR or SGA)
  • overwhelming infections (it is also called “sepsis”)
  • birth with a low Apgar Score (Apgar Score explained here)

Features of Necrotic Enterocolitis in Newborns


Whenever we suspect Necrotic Enterocolitis in a baby, doctors will review clinical symptoms, perform imaging studies of the abdomen, and do some laboratory tests.

Clinical presentation

Frequently, the first sign of Necrotic Enterocolitis is the development of feeding intolerance. Premature newborns will have increased gastric residuals after tube feedings, bloody stools, and abdominal distention. When the disease becomes more advanced, babies present with increased sleepiness or lethargy, apneas (pause in breathing), heart rate drops, abdominal tenderness, and discoloration of the skin on the abdomen. 

The sickest babies will also have temperature instability and abnormally low blood pressure, which frequently are signs of overwhelming infection (sepsis) and a bowel perforation.

Imaging studies (X-ray and Ultrasound)

We can use an abdominal X-ray and abdominal ultrasound to aid us in the diagnosis of NEC. However, an abdominal X-ray remains the most popular technique. 

Pneumatosis (presence of air within the bowel walls) is diagnostic if found on an abdominal X-ray of the baby who is suspected of having NEC. 

Other radiologic (X-ray) findings in NEC include:

  • ileus – lack of peristalsis or intestinal movements
  • dilated intestines
  • presence of air in the portal vein (blood vessel in the liver)
  • free air in the abdominal cavity which is a result of ruptured bowel loops

Abdominal ultrasound allows doctors to evaluate the presence of fluid, the thickness of intestinal walls, and blood flow to intestines. Ultrasound is a less popular method of assessing babies with NEC as it requires more experience from the examiner.

Laboratory studies

Laboratory tests are an essential part of the diagnostic process for detecting NEC. The most commonly conducted tests are blood cultures, blood counts, and coagulation studies. 

Blood culture is done to confirm or rule out the presence of bacterial infections. If positive, it will allow us to choose the best antibiotics for the treatment. 

Blood counts (CBC), in babies with NECwill often show anemia, low or high white cell counts, and low platelet levels. These abnormalities are not specific only to the NEC diagnosis but can support our suspicion of it in the patient. 

Coagulation studies look at levels of relevant clotting indices in the blood. The sickest babies diagnosed with NEC will have these abnormalities and may require plasma or platelet transfusions to correct them. 

Staging of NEC

In the effort to describe different presentations and prognoses in NEC, clinicians classify each case of NEC into one of the three stages.

Stage 1 – Suspected NEC (mild NEC)

Babies have abdominal distention, bloody stools, and emesis or gastric residuals. On Xray, we will see signs of ileus and bowel loops dilation.

Stage 2 – Proven NEC (moderate NEC)

Clinically, the baby will present with abdominal tenderness. Laboratory tests will show acidosis (more acid in the blood) and low platelet counts. An x-ray will show pneumatosis and/or the presence of gas in the portal vein.

Stage 3 – Advanced NEC (severe NEC)

In addition to previously described clinical features, the baby is also likely to have low blood pressure, low white cell counts, low platelet counts, and significant acidosis in the blood. An X-ray in advanced NEC will show evidence of ruptured bowel loops with free air in the abdominal cavity. 

Differential diagnosis

As with any other medical diagnosis, whenever we suspect Necrotic Enterocolitis, we need to consider other diagnoses to avoid mistakes. Below, I will describe some of the conditions that may mislead us.

Anal fissure – Babies with anal fissure may present with bloody stools, and bloody stools may occur in NEC as well. 

Milk allergy – Milk allergy is a rare occurrence in a baby before 6-8 weeks of age, but sometimes it can happen, particularly in babies fed with formula. Those affected babies may have abdominal distention, frequent stools, and bloody stools.

Overwhelming infection or sepsis – Babies with an ongoing infectious disease may present with apnea, low blood pressure, and feeding intolerance, including ileus on abdominal X-ray.

Spontaneous intestinal perforation – It is a sporadic condition. It may occur especially in babies born with birth weights of less than 1500 grams. The differentiation from NEC is that there will be no pneumatosis (air in the intestinal wall) on the X-ray. 

Appendicitis – Another rare condition in newborns that may lead to perforation and infection in the abdominal cavity (peritonitis).

Viral or Bacterial Enteritis – Infection of the gastro-enteric tract may present itself with abdominal distention, frequent stools, bloody stools, and deterioration of the general condition. 

Treating NEC

There is no specific treatment for NEC. Our approach will vary depending on the severity of the condition and will involve multiple steps described below. 

Supportive care

Babies with diagnosed or suspected Necrotic Enterocolitis will not receive any feedings (we say that we put them NPO = “nil per os”). In addition, we often place a large size plastic tube in their stomach and connect it to intermittent suction to evacuate excessive gas from the abdomen and allow bowel loops to rest. 

Most babies will not be receiving any milk by mouth for 10-14 days. Therefore, we place a central intravenous line so we can give them appropriate fluids and nutrition. 

Many newborns with NEC need to be placed on ventilators with supplementary oxygen, receive medications to support their blood pressure, and are given transfusions of blood products.

Empiric antibiotics

Empiric use of antibiotics in the treatment of NEC is a must. Approximately 30% of babies diagnosed with NEC will have positive blood cultures, which means that they will have actual bacteria identified in their blood. In remaining patients, bacterial overgrowth in the intestines is likely to cause damage to the intestinal mucosa leading to local inflammation; therefore, the use of antibiotics is also wise. 

Close monitoring

Necrotic Enterocolitis is always evolving and may get much worse very quickly. Doctors monitor all babies very closely to detect early changes in their condition and acute complications requiring changes in the treatment approach. 

Monitoring babies with NEC almost always will include:

  • frequent physical examinations with abdominal girth measurements (stable or decreasing abdominal circumference is a positive sign)
  • regular abdominal X-rays – certain findings on X-ray may warrant urgent surgical consult and operation
  • continuous monitoring of respiratory and heart rates, blood pressure and oxygen saturation (that is done using bedside monitors always present in NICU)
  • blood tests (levels of electrolytes, blood counts, clotting factors)

Surgical procedures

Babies with the most severe form of Necrotic Enterocolitis need surgical treatment. The absolute indication for the surgical approach is perforated bowel with free air present in the abdominal cavity. Other indications are less specific and will vary depending on the experience of the center where your baby is being treated. Approximately 50% of babies with NEC require surgical treatment (Source).

There are two surgical techniques available to us: open abdomen surgery (laparotomy) and placement of the drain (Penrose drain).

Surgeons and neonatologists have been studying both methods over the last decade, trying to establish which one may be better; however, so far, this question has not been answered adequately yet. It seems that both approaches have similar rates of death and complications, but studied sample sizes were not big enough to say that with certainty.

Laparotomy or open abdomen surgery 

The baby needs to be put under general anesthesia. A surgeon cuts through all the layers of the abdominal wall, cleans the abdominal cavity, resects dead pieces of the bowel loops, and usually creates ostomy. Ostomy is an opening on the abdomen created by the surgeon to allow intestinal contents to come out. In NEC, the purpose of ostomy is to let the rest of the bowel loops heal and recover over time. 

Once baby recovers from the NEC and bowel loops healed, the baby will need another surgery to close ostomy and return continuity of the intestines so stool can be expelled through the anus again. 

Penrose drain 

This method is the only one that can be offered to babies that are too unstable to undergo surgery under general anesthesia. Penrose drain placement can be done using only local anesthesia at the bedside. A surgeon can place a Penrose drain only under local anesthesia in the NICU instead of the operating room. The Penrose drain is a small tubing that can be put into the abdominal cavity to decompress abdomen and to irrigate and drain infectious contents. 

If the baby survives the acute phase of NEC, Penrose drain is removed, and doctors evaluate the baby’s gastrointestinal tract to be sure that the baby can be safely started on feedings. 

Outcomes in babies with a diagnosis of NEC

Despite many improvements in the care of babies affected by NEC, still Necrotic Enterocolitis is a condition associated with significant mortality and many short term and long term complications. In addition, survivors tend to have less favorable developmental outcomes when compared to peers who did not have the NEC diagnosis. 


Necrotic Enterocolitis may be responsible for up to 10% of all deaths in advanced NICUs caring for all types of premature babies. Data gathered from 655 US-based centers between 2006 – 2010 showed an overall 28% mortality for babies diagnosed with NEC (Source). 

Mortality is higher for smaller and more premature babies and for those who require surgical treatment. 

Table 3: Mortality rates for different birth weights. Data from a paper published in 2009 by Fitzgibbons. Data covers years: 2005-2006.

Birth WeightMortality if having NEC
1250 – 1500 grams16%
1000 – 1250 grams21%
750 – 1000 grams29%
501 – 750 grams42%


Babies affected by NEC may develop acute and chronic or long term complications.

Acute complications (short-term)

  • Infections – up to 30% of babies with NEC will have confirmed generalized systemic infection. Many will also develop pneumonia, peritonitis, or abscesses.
  • Respiratory problems – many babies with the diagnosis of NEC will have to be placed on a ventilator even if they previously had been weaned off it
  • Heart failure and low blood pressure – some babies need medications to maintain normal levels of blood pressure
  • Excessive Bleeding – some babies will need platelet or plasma transfusion to improve their clotting ability
  • Metabolic abnormalities in the blood such as acidosis, low glucose, low or high sodium levels, and many others
  • Kidney failure – due to infections, fluid imbalances, or clotting abnormalities, the baby may develop an abnormal renal function

Long term complications

The most important long term complications of NEC are the conditions that can impact absorption, patency, or peristalsis of the intestines. 

10%-35% of babies with NEC diagnoses will develop strictures. Strictures are scars built of connective tissue, often compressing bowel loops from the outside, causing a narrowing and decreasing their patency. Therefore, they may contribute to feeding intolerance and, in some cases, cause complete obstruction. 

Short bowel syndrome – In babies with severe NEC, a surgeon may need to remove a significant portion of dead bowel loops. If the baby ends up with less than 25% of the normal length of intestines, such a baby may develop short bowel syndrome. 

Babies with short bowel syndrome will have significant nutritional problems due to the inability to absorb essential nutrients from milk and later on from solid food. Those babies will be affected by many medical issues, including very poor physical growth. 

Motor and intellectual Development

Infants with NEC diagnosis are at increased risk of having growth failure, cerebral palsy, intellectual disability, and vision problems. The risk of those problems may be as high as twice that for matched newborns who did not have NEC. 

It also seems that the severity of NEC plays a role since babies who required surgical treatment tend to have more poor outcomes than the babies who were treated only medically. 

Prevention of Necrotic Enterocolitis

The most obvious way to avoid NEC is to prevent premature birth. If you are still pregnant and worried about this condition, read my article on the causes of premature birth here. If you are already in early labor, you may want to talk to your obstetrician, whether you should receive Bethametasone. 

Steroid medications such as Bethametasone or Dexamethasone when administered to women in premature labor at least 24-48 hours before the actual birth of the baby, decrease rates of Acute Respiratory Distress, mortality, Intraventricular Hemorrhage, ROP and Necrotic Enterocolitis.

If your baby is already born and treated in the NICU, neonatologists try to follow specific practice guidelines that are believed to decrease rates of NEC. One approach that is probably most powerful is providing breast milk to all premature babies instead of the formula. 

General neonatal practice suggestions

Most doctors who treat premature babies believe that the practices described below decrease rates of NEC. However, not all of them are well documented by research and evidence. 

  • avoidance of prolonged antibiotic treatment courses
  • avoidance of medications that decrease acidity in the stomach (so-called H2 blockers)
  • using feeding protocols in the NICU (being careful about daily increases in feeding volumes)
  • treatment of polycythemia
  •  exclusive use of breast milk for feedings
  • use of probiotics (in the USA it is still controversial)

Use of human milk

If somebody asked me what one best medicine used in NICU is, I would quickly answer; it is breast milk. Breast milk is a miracle solution for premature babies. Exclusive use of breast milk for feedings most likely contributes to lower mortality rates, infections, NEC, and faster discharge home from NICU. I encourage you to read my three other articles focused on the benefits of breastmilk for babies, benefits for mothers, and contraindications to breastfeeding.

When compared to the bovine protein-based formula, human milk has been shown to decrease the risk of Necrotic Enterocolitis. The effect is dose-dependent, meaning: when the higher percentage of total feeding volumes is given as breastmilk, the risk of developing NEC by the baby is lower. 

If a mother is unable to provide breast milk for her baby, we can use breast milk obtained from the breastmilk bank. Donor breastmilk also has been shown to have protective effects on the risk of NEC and is highly recommended for micro-preemies and extremely premature babies.

Use of probiotics 

Probiotics are live bacteria that can be given to babies in order to facilitate positive health outcomes, including a decrease in the rate of Necrotic Enterocolitis.

Despite numerous studies that have been conducted so far, many questions and concerns remain and prevent most US neonatologists from using them.

Many studies showed benefits for mortality rates and NEC rates in newborns, but those positive results were inconsistent for the most vulnerable groups, such as micro-preemies.

Questions remain regarding an appropriate product containing probiotics, dosage, indications for it, and duration of treatment. Additional concerns are that use of probiotics in most vulnerable patients such as micro-preemies and extremely premature babies may cause severe infection (sepsis).

Questions to ask if your baby is in the NICU and has Necrotic Enterocolitis

  1. How certain are you about NEC diagnosis?
  2. Which stage of NEC does my baby have?
  3. What can I do for my baby? 
  4. Do you have a pediatric surgeon in place so my baby could receive optimal treatment when required?
  5. If you do not have a pediatric surgeon available on site, should we transfer my baby to another institution as soon as the baby is stable enough to undergo such transport?
  6. How long will my baby be on antibiotics?
  7. How long do you expect to keep my baby NPO (without any milk for feedings)?
  8. Did my baby develop any acute complications due to NEC?

If you have a premature baby born before 32 weeks receiving treatment in the NICU right now, I encourage you to explore my book “Babies Born Early


This article is only for general information purposes. It should not be viewed as medical advice. There is a chance that information here may be inaccurate. It would be best if you always discussed all health-related matters with your doctor before making any decisions that may affect your health or health of your family members.


Dr.Wisniewski is a board-certified pediatrician and neonatologist with over 20 years of clinical experience in the USA. He authored the book: "Babies Born Early - A guide for Parents of Babies Born Before 32 Weeks" Dr.Wisniewski loves educating parents on various health conditions affecting their newborn babies and children.

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