Introduction

Necrotising enterocolitis (NEC) is a gastrointestinal problem that occurs mostly in premature babies, causing the intestinal tissue to become inflamed and die. NEC is the most common surgical emergency in premature babies and is becoming a more common issue. However, this is likely due to the fact that more premature babies are surviving in this modern day age.¹  

Statistics show that 9 out of 10 babies who get NEC are born early. As a result, it is important to address why preterm infants are affected by NEC. This article is going to explore and discuss the physiological, immunological, and microbiological reasons behind this susceptibility.

What is Necrotising Enterocolitis?

NEC is a condition whereby intestinal tissue in newborn infants becomes inflamed and dies. Furthermore, this can lead to perforations (holes) of the intestine forming. As a result, this allows the contents of the intestine, which contain bacteria, to leak into the abdomen, causing serious infections. 

NEC mostly affects babies who are:² 

• Premature
• Tube fed through their stomach
• Born with a weight of less than 2.5kg

Common signs and symptoms

There are various symptoms of NEC. 

Some symptoms include:³

• Abdominal bloating: Swelling or bloating of the abdomen is a key indicator of NEC
• Intolerance to feeding: Babies may show signs of refusing to feed or show signs they are experiencing discomfort while feeding
• Vomiting: If babies are vomiting, this may mean that there could be an obstruction within the intestinal tract
• Lethargy: Babies with NEC may appear tired or inactive
• Temperature: A baby's temperature may fluctuate
• Blood in stool: There may be the presence of blood in stool of babies with NEC, if blood is present in the stool, then a healthcare provider should be informed immediately

Incidence and mortality rates

Studies report that the overall mortality rate for infants with NEC is 23.5%. 

However, those with surgical NEC pose a greater risk of mortality, ranging from 30 to 50%.⁴  

Risk factors

Risk factors for NEc include:

• Prematurity
• Abnormal gut microbiota
• Feeding 
• Birthing Factors 
• Maternal Risk Factors 

Prematurity 

Prematurity paired with a low birth weight (LWB) is two of the main risk factors for developing NEC. Statistics have shown that NEC affects 5-7% of all preterm babies, but 10-12% of these babies born weigh less than 1500g.^5,6 

In addition to this. Research has shown that the chances of NEC occurring in babies born at 24 weeks gestation were 11% and decreased to 0.5% for babies that were born at 31 weeks gestation. Furthermore, full-term infants can develop NEC, but it is a lot more rare for this to happen.⁷

Abnormal gut microbiota 

Gut Dysbiosis is another important contributor to the development of NEC in babies. This means a low count of beneficial gut microbes paired with a low diversity of bacteria in the gut. This promotes the growth of harmful bacteria in the gut, producing an inflammatory response that can lead to perforations..   

Feeding

Studies carried out have highlighted the importance of feeding in developing NEC. Breast milk feeding has been shown to be protective, and therefore, when unavailable, formula is given instead. Formula has been shown to increase the risk of developing NEC compared to donor breast milk.⁸

Birthing factors

Perinatal events such as placental abruption can lead to the baby becoming starved of blood and oxygen. As a result, the baby can become deprived of oxygen and nutrients for growth.  

Maternal risk factors

Substance abuse through taking illicit drugs and contracting an HIV positive status can increase the likelihood of NEC developing in a mother’s baby after birth. 

Current management strategies 

• No food or drinks orally in order to rest the bowel
• Fluids and antibiotics given intravenously to fight off infection and stay hydrated
• If babies are not responding to antibiotics or have been on course for a prolonged length of time, then antifungals are considered
• Vasopressors such as naloxone and dopamine may be beneficial to very ill babies, for support with blood pressure 
• Surgery may be necessary for perforated or deteriorating bowels. Intubation/ventilation
• Babies can usually begin to oral feed again after 7-10 days if showing improvements

Prevention of NEC 

Feeding babies who are at risk of developing NEC with breast milk can help prevent the likelihood of them from developing it. To begin with, babies should be fed small amounts that are gradually increased over time. If there are any signs of anaemia, low oxygen saturations and polycythemia, these should be treated immediately. Additionally, things such as antibiotics and acid-suppressing medications should be avoided. 

Probiotics containing bifidus infantis and lactobacillus acidophilus can help to prevent babies from developing NEC. However, further research is required to discover the optimal dosing and appropriate strains that are needed before they are taken routinely.^9,10

Women who are at risk of a preterm birth may be given corticosteroids during pregnancy, in order to help prevent the likelihood of their baby developing NEC.¹¹

Conclusion

This article has explored the role of prematurity in developing NEC, a condition whereby intestinal tissue becomes inflamed and dies, causing perforations, meaning bacteria leak into the abdomen, causing infections. This condition can occur in full-term babies; however, it is significantly more likely to occur in premature babies. 

Studies carried out have indicated that 9 out of 10 babies who develop NEC are born before the 37th week and weigh less than 2.5kg. Furthermore, statistics have shown that babies born before 24 weeks had an 11% chance of developing NEC, and this decreased to 0.5% for babies born at 31 weeks gestation. 

As a result, it is evident that preterm babies are more likely to develop NEC. Common signs and symptoms of NEC range from bloating, lethargy and resistance to feeding to vomiting and bloody stool. There are many risk factors of NEC, such as maternal factors like drug use and a positive status, or birthing factors such as placental abruption, causing loss of blood and oxygen, depriving the baby of nutrients for growth. 

Additionally, another important risk factor in developing NEC is that babies being formula fed compared to breastfed can increase the chances of developing NEC. This indicates human breastfeeding can be protective for babies that are at high risk of developing the condition. 

Further prevention includes taking probiotics (however, more research is required for optimal dose and strain) and corticosteroids. 

In conclusion, prematurity plays an important role in the development of NEC in babies, and therefore, common signs and symptoms should be acknowledged immediately while carrying out appropriate prevention methods. 

FAQ’s

What causes necrotising enterocolitis?

Factors that cause NEC in preterm babies include: 

• A decreased  blood flow to the lining of the bowel
• Preterm babies have immaturity of the bowel
• The likelihood of infections in preterm babies is greater, and they are unable to fight this off as well as full-term babies

How do I know if my baby has this condition?

Your baby may seem slightly unwell during the early stages. However, as NEC progresses, you may start to notice other things such as:

• Abdomen becoming swollen and tender
• Bloody stools or your baby stops passing stool altogether
• Green vomit
• Showing signs of infection such as sleepiness
• High or low temperature
• Skin on the abdomen is becoming red
• Breathing problems

These are some of the first signs that a doctor will look out for when suspecting NEC in your baby. However, they will need to carry out x-rays in order to help with a diagnosis of the condition.. 

How is this condition treated?

Surgery is not required in a lot of cases of NEC. Food is given intravenously in order to rest the bowel. Furthermore, a course of antibiotics is provided to treat any infection. This course will usually last around 7-10 days. 

However, if any perforations (holes) have formed in the bowel or your baby is unresponsive to treatment, then surgery may be required.