Products Liability Law Daily Wrap Up, EXPERT EVIDENCE—BABY PRODUCTS—N.D. Ill.: Expert’s testimony did not apply to preterm infant; Abbott Labs thus entitled to summary judgment in baby formula litigation, (Aug 15, 2025)

By Nicholas Kaster, J.D.

The stark absence of epidemiological evidence supporting the expert’s opinions when applied to infants like the one in this case “cannot be ignored,” said the court.

Products liability claims against Abbott Laboratories in multi-district litigation over injuries to a premature baby who consumed its infant baby formula failed to survive summary judgment. A federal district court in Illinois excluded the testimony of an epidemiologist who opined that the formula substantially increases the risk of injury to preterm infants. The court held that the expert’s conclusions did not fit the facts of the case because they did not apply to preterm infants born at this baby’s gestational age and weight. Without this expert’s testimony, the infant’s mother, the plaintiff, could not prove that Abbott’s formula caused the baby’s injuries (In re: Abbott Laboratories Preterm Infant Nutrition Products Liability Litigation, No. 22 C 05356 (N.D. Ill. Aug. 14, 2025)).

Background. The baby was born moderately premature (32 weeks gestational age) with a low birth weight (2,095 grams) and was immediately admitted to the NICU. Two days after birth, his physicians began feeding him with Similac Special Care 20, a cow’s-milk-based infant formula (CMBF) developed by Abbott Laboratories. After a week of being fed CMBF, the baby presented signs of necrotizing enterocolitis (NEC), a devastating illness affecting preterm infants, and required surgery removing a section of his intestine. Like hundreds of other plaintiffs in this multi-district litigation (MDL), the baby’s mother alleged that her child’s NEC was caused by exposure to Abbott’s preterm formula. Her complaint alleged failure-to-warn and design defect claims under Maryland law. Specifically, she claimed that Abbott was aware of the increased risk of NEC from CMBF but failed to take steps to improve the formula or otherwise warn doctors and parents of the risk. On September 30, 2022, the case was transferred to a federal district court as part of the MDL and the case was selected as one of four bellwether trials.

The mother’s claims hinged on the expert opinion of an epidemiologist who has opined (for cases across the MDL) that CMBF substantially increases the risk of NEC in preterm infants. Abbott moved to exclude the testimony of the epidemiologist, asserting that his conclusions did not apply to preterm infants born at this baby’s gestational age and weight. Abbott further moved for summary judgment, noting that the mother could not prove that Abbott’s formula caused her baby’s NEC without the expert’s testimony.

Expert’s testimony. The expert was a Professor and Director of the Division of Epidemiology and Clinical Research in the Department of Pediatrics at the University of Minnesota Medical School. His report found that, using a meta-analysis of randomized control trials (RCTs), predominantly CMBF diets increase the risk of NEC by 60% when compared to human milk diets. He further opined that the association between NEC and CMBF is causal, applying the Bradford Hill factors for determining causality.

The expert’s testimony was central to the mother’s theories of causation, the court noted. His epidemiological opinion served as the basis for the opinions of the mother’s other general causation expert, as well as her specific causation expert. Importantly, the expert’s report discussed the risk of NEC as applied to all preterm infants and did not touch on the applicability of his opinion to infants within specific brackets of gestational age and birthweight. In his deposition, the expert suggested that an “extrapolation” could be done to apply his conclusions to infants above 2,000 grams and 32 weeks gestational age, but admitted that he performed no such analysis himself.

“Fit” of expert’s testimony. The issue here, said the court, was not whether the expert’s conclusions were reliable, but whether his testimony “fits” the facts of the case such that there was a “valid scientific connection to the pertinent inquiry.”

Abbott argued that the expert relied exclusively on studies that either excluded infants like the one in this case from the study population or, by his admission, found no association between CMBF and NEC. The mother offered several reasons why his opinion should nonetheless be admitted despite these limitations, none of which the court found persuasive.

First, she argued that because the expert was a general causation expert, he need not opine as to whether CMBF caused NEC in her baby’s specific circumstances. But this missed the point, said the court. Abbott’s argument was not that the expert did not offer a specific causation opinion, but that his general causation opinion did not apply to infants like the one here. Indeed, said the court, the expert appeared to admit that a further step, what he called an “extrapolation,” would be required for his conclusions to be applied to infants weighing 2,000 grams and of 32 weeks gestational age at birth. He was not required to perform this extrapolation himself in his original report; a case-specific expert could perform this extrapolation or could have directed the expert to supplement his report in preparation for testifying in this case. But absent any testimony that the expert’s estimation of a 60% increased risk of NEC from CMBF and Bradford Hill analysis applied to infants like the one in this case, the mother lacked the crucial connective tissue between the expert’s testimony and the facts of her case.

Next, the mother suggested that the studies that included infants like her baby supported application of the expert’s testimony to this case. She pointed to two studies in particular. But the court found that neither adequately supported her case. One was a case control study that, while including infants in the same gestational age range and potentially supporting his conclusions, post-dated the expert’s report and was not considered in his analysis. The other was a case control study that was included in his report and would have included infants like the one here. But, when questioned about the study during his deposition, the expert admitted that it found no association between CMBF and NEC. Abbott did not “ignore” this study as the mother suggested, but properly noted that its results did not support the fit of his opinions to this case.

Finally, the mother contended that epidemiology is the “study of populations” rather than individuals, and that the expert’s opinion should be accepted as applying to all preterm infants. It is true that the expert’s opinions have application across a range of infants of different birthweights and gestational ages, the court acknowledged, and that he described the scope of his opinion in his report as applying to “preterm infants” generally. But recognizing that epidemiology is the study of populations, the relevant “population” for any epidemiological opinion must be derived from the populations of the underlying studies, not the ipse dixit of the expert. While the expert himself did not discriminate between birthweight and gestational ages in preparing his report, said the court, the same could not be said for the studies that supported his opinions.

Had there been even one RCT that would have included the baby here in its population and supported an association between CMBF and NEC, this might be a different case. But the “stark absence of epidemiological evidence” supporting the expert’s opinions when applied to infants like the one here “cannot be ignored,” said the court.

Accordingly, the court concluded that there was insufficient evidence to tie the expert’s testimony to the facts of the case.

The mother sought leave to supplement the expert’s testimony to provide this evidence, but the court concluded that it was neither feasible nor fair to Abbott to allow her to supplement the expert’s report at this late juncture. As to feasibility, the court was not persuaded that the “extrapolation” the expert described (if possible at all)—not to mention Abbott’s rebuttal evidence—could be prepared without significantly delaying trial, complicating the timeline of future bellwether cases as currently scheduled. But even if such a supplement were feasible, said the court, it would not be fair to Abbott to allow the mother to attempt to cure the defects in her case at this point in the litigation.

Without the expert’s testimony, the mother was unable to meet her burden of showing causation to survive summary judgment. Accordingly, Abbott’s motion for summary judgment was granted.

The case is No. 22 C 05356.

Judge: Pallmeyer, R.

Attorneys: Charles Andrew Childers (Levin, Papantonio, Proctor, Buchanan, O'Brien, Barr, & Mougey, PA) for Keosha Diggs. James F. Hurst (Kirkland & Ellis LLP) for Abbott Laboratories and Abbott Laboratories Inc.

Companies: Abbott Laboratories; Abbott Laboratories Inc.

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