When a premature baby develops necrotizing enterocolitis, or NEC, after being fed cow’s milk-based formula, the parents face a medical nightmare. NEC is a devastating intestinal disease that can kill a newborn or leave the child with permanent digestive problems. In recent years, hundreds of families have filed lawsuits against formula manufacturers, claiming that products like Similac and Enfamil caused their babies’ injuries. These cases fall under mass tort and class action liability, but each family still has to prove the same basic thing in court: the formula actually caused the disease. That is not as simple as it sounds.
Causation is the heart of any injury claim. In plain terms, the parents must show that the formula was the reason their baby got NEC. Not just that the baby was fed formula and later got sick. They have to convince a judge or jury that the formula played a significant role in triggering the disease. This is different from a product defect case where a car part breaks and the injury is obvious. Here, the injury develops inside a fragile infant, and there can be many contributing factors. Prematurity itself is the biggest risk factor for NEC. So the first hurdle is separating the natural dangers of being born early from the added risk posed by the formula.
To meet this burden, plaintiffs rely on two main types of evidence. The first is statistical and epidemiological research. Numerous peer-reviewed studies have shown that premature infants who are fed exclusively with cow’s milk-based formula are at a substantially higher risk of NEC than those who receive human breast milk. Some studies indicate that the risk is three to ten times higher for formula-fed preemies. This kind of data does not prove that a specific baby’s NEC was caused by formula, but it establishes a general link. Courts allow this evidence to support the idea that the product is capable of causing the disease. That is a major step in any product liability case.
The second type of evidence is medical expert testimony. In almost every NEC case, the parents bring in a neonatologist or pediatric surgeon who explains to the jury how the formula works in the immature gut. The expert describes how cow’s milk proteins and certain additives can damage the intestinal lining of a preemie, allowing bacteria to invade and trigger NEC. The expert will also review the baby’s medical chart, noting when formula was started, how much was given, and when symptoms appeared. If the timeline fits, the expert can state with reasonable medical certainty that the formula was a cause of the disease. That specific phrase matters. Courts require that experts say the product was a cause, not just a possibility.
Defense lawyers, of course, fight back. They will argue that NEC happens even in babies who only receive breast milk, and that no one can point to a definitive test proving causation for an individual infant. They will bring their own experts to say that the baby’s prematurity, infection, or other medical conditions were the real cause. They will also emphasize that the formula is approved by the FDA and has been on the market for decades. This creates a battle of the experts, which is normal in modern mass tort litigation. The jury must decide which explanation is more convincing.
One legal concept that often comes up in these cases is the difference between a risk factor and a direct cause. Doctors may tell parents that NEC has many causes, and formula is just one of them. But the law does not require that the formula be the only cause. It only requires that the formula was a substantial factor in bringing about the harm. So even if a baby had other risk factors, a plaintiff can still win if they show that the formula materially increased the risk and likely contributed to the disease. This is called the substantial factor test, and it makes these cases more winnable for families than many people expect.
Another issue is the lack of explicit warnings on the labels. Parents often argue that they would have never allowed formula to be used in the neonatal intensive care unit if they had known about the increased risk of NEC. The manufacturers had this information from studies and internal documents, but they failed to warn hospitals and parents. This is a separate claim, but it ties back to causation. If the warnings had been adequate, the baby would have received donor milk or a different feeding strategy, and the NEC would likely not have occurred. This is called the heeding presumption, where the court assumes the parents would have followed the warning if one had been given.
In recent years, juries have awarded massive verdicts in a few NEC cases. But many more cases are still pending, and the outcome of future trials will depend heavily on solid causation evidence. The science is strong, but it is not absolute. That is why the legal system relies on experts and statistical data. For parents, the key to a successful claim is not just showing that the formula is dangerous. It is proving that the formula was dangerous for their specific child. That requires careful medical records, knowledgeable experts, and a clear explanation that a jury can understand. Without causation, there is no claim. With it, the manufacturers can be held accountable.
