Necrotizing enterocolitis (NEC) is a severe intestinal inflammation that mainly affects premature or ill newborns. The condition can result in tissue damage and serious complications. Feeding with breast milk instead of formula can significantly lower the risk of developing NEC.
Necrotizing enterocolitis, commonly known as NEC, is a medical condition that causes intestinal inflammation in newborns. While it can affect any infant, premature or ill babies are at greater risk.
Inflammation caused by NEC can lead to several complications, such as organ problems, intestinal tissue death, bowel obstruction, nutrient malabsorption, vitamin deficiencies, feeding difficulties and bacteria overgrowth. Bacteria can enter holes in the intestine, leading to deadly infections, such as sepsis.
Treatments for NEC include antibiotics and surgery. Doctors may remove a part of the baby’s bowel and check for holes in the intestinal tract. Babies will stay in the hospital for observation and treatment. Once babies are eating and not losing weight, they may be able to go home.
Babies with severe or worsening NEC may develop generalized swelling or fluid retention and low blood sodium levels. As NEC worsens, babies develop kidney problems and excessive potassium in the blood.
A study funded by the National Institutes of Health, published in the Journal of the American Medical Association, found that premature babies given donated human milk had a significantly lower risk of developing NEC than those fed formula.
Specifically, only 4.2% of the babies who received human milk developed NEC, while the rate was 9% for those on formula.
The study included 483 babies born before 29 weeks of pregnancy or weighing less than 2.2 pounds. This study provides substantial evidence that using donated human milk can help protect premature babies from NEC.
One of the first studies to link baby formula to NEC was a 1990 study that found premature babies fed formula were up to 10 times more likely to develop NEC. Breast milk didn’t show the same risk, and researchers have found that human breast milk may reduce the risk of NEC.
Researchers have hypothesized that antibodies, growth factors and immune cells in breast milk may protect a premature baby’s gut, which may prevent NEC. Cow’s milk baby formulas may be more challenging to digest and could cause inflammation that contributes to NEC, but more studies are needed.
Premature babies and babies who are sick or born with birth defects have a higher risk of developing NEC. It’s most common in preemies born before 37 weeks, according to the National Organization for Rare Disorders.
Formula feeding with cow’s milk baby formula can further increase the risk.
About one in 1,000 premature babies and about one in 10,000 full-term babies may get NEC. Most babies develop NEC while still in the hospital.
In September 2024, the Necrotizing Enterocolitis in Preterm Infants Working Group published a report outlining several research priorities.
The working group noted that NEC is a complex condition influenced by various risk factors. They stressed the importance of research to improve human milk production, enhance its positive qualities and address the inequalities in access to donor milk.
Feeding premature babies mother’s milk or human milk from a donor may lower the risk of NEC.
Cow’s milk formulas — such as Enfamil, Similac and other brands — have the greatest chance of causing NEC compared to breast milk. A July 2022 animal study in Frontiers in Pediatrics found that some preterm baby formulas may be more damaging to the gut than others.
“Our findings indicate that not all preterm formulas are the same, and different formulations can have varying effects on intestinal inflammation, apoptosis and microbiome composition,” the study authors wrote.
For example, researchers found that Similac Special Care caused more intestinal injury than NeoSure. Similac Special Care is a popular formula for preemies in the neonatal intensive care unit because it’s designed to help them grow and heal. NeoSure is a catch-up growth formula for premature babies who have already gone home from the hospital.
In February 2022, Abbott issued a baby formula recall for Similac, Alimentum and EleCare after some babies died of Cronobacter sakazakii infections. All affected formulas came from Abbott’s Sturgis, Michigan, plant.
Abbott closed the plant to investigate bacterial contamination. The U.S. Food and Drug Administration has since inspected the plant and found Cronobacter in certain areas around it but not in the product samples it tested. The recall and plant closure contributed to a national baby formula shortage, but the plant is back open.
In October 2022, Abbott issued another recall for certain ready-to-feed liquid formula lots because some bottle caps might not have been appropriately sealed. Improperly sealed bottles could cause spoilage, which could lead to stomach problems in children who consume the formula.
Brands in this recall include Similac Pro-Total Comfort, Similac 360 Total Care, Similac 360 Total Care Sensitive, Similac Special Care 24, Similac Stage 1, Similac NeoSure, Similac water (sterilized) and Pedialyte electrolyte solution.
Parents whose premature babies developed NEC after consuming Enfamil or Similac have filed baby formula lawsuits against manufacturers Abbott Laboratories and Mead Johnson.
Lawsuits claimed that the companies knew or should have known that cow’s milk baby formula could cause NEC in preterm infants. However, manufacturers continued to sell the formula and failed to warn parents and doctors.
In August 2022, judges consolidated baby formula lawsuits nationwide in Illinois multidistrict litigation. As of March 2025, 663 cases were pending.
The first bellwether trial is scheduled for May 2025.
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