As if the birth of a premature baby isn't stressful enough, there are a number of diseases premature babies can experience within the first weeks of life. Necrotizing enterocolitis (NEC) is one of them. "Necrotizing" means the death of tissue, "entero" refers to the small intestine, "colo" to the large intestine, and "itis" means inflammation. But knowing what the words mean is only the start of understanding this infant disease.

What Is Necrotizing Enterocolitis?

A gastrointestinal disease that mostly affects premature infants, NEC involves infection and inflammation that causes destruction of the bowel (intestine) or part of the bowel. Although it affects only one in 2,000 to 4,000 births, or between 1% and 5% of neonatal intensive care unit (NICU) admissions, NEC is the most common and serious gastrointestinal disorder among hospitalized preterm infants.

NEC typically occurs within the first 2 weeks of life, usually after milk feeding has begun (at first, feedings are usually given through a tube that goes directly to the baby's stomach). About 10% of babies weighing less than 1,500 grams (3 lbs., 5 oz.) experience NEC. These premature infants have immature bowels, which are sensitive to changes in blood flow and prone to infection. They may have difficulty with blood and oxygen circulation and digestion, which increases their chances of developing NEC.

What Causes It?

The exact cause of NEC is unknown, but several theories exist. It is thought that the intestinal tissues of premature infants are weakened by too little oxygen or blood flow, and when feedings are started, the added stress of food moving through the intestine allows bacteria that are normally found in the intestine to invade and damage the wall of the intestinal tissues. The damage may affect only a short segment of the intestine, or it may progress quickly to involve a much larger portion.

The infant is unable to continue feedings and starts to appear ill if bacteria continues to spread through the wall of the intestines and sometimes into the bloodstream. He may also develop imbalances in the minerals in the blood. In severe cases of NEC, a hole (perforation) may develop in the intestine, allowing bacteria to leak into the abdomen and causing life-threatening infection (peritonitis). Because the infant's body systems are immature, even with quick treatment for NEC there may be serious complications.

Other factors seem to increase the risk of developing NEC. Some experts believe that the makeup of infant formula, the rate of delivery of the formula, or the immaturity of the mucous membranes in the intestines can cause NEC. (Babies who are fed breast milk can also develop NEC, but their risk is lower.) Another theory is that babies who have had difficult deliveries with lowered oxygen levels can develop NEC. When there is not enough oxygen, the body sends the available oxygen and blood to vital organs instead of the gastrointestinal tract, and NEC can result. Babies with an increased number of red blood cells (polycythemia) in the circulation also seem to be at higher risk for NEC. Too many red blood cells thicken the blood and hinder the transport of oxygen to the intestines.

NEC sometimes seems to occur in "epidemics," affecting several infants in the same nursery. Although this may be due to coincidence, it suggests the possibility that it could in some cases be spread from one baby to another, despite the fact that all nurseries have very strict precautions to prevent the spread of infection.