A Missouri judge has ordered Abbott Laboratories and Reckitt Benckiser unit Mead Johnson to face a new trial over allegations that they failed to warn a mother about the risks of their specialized baby formulas for premature infants,

Back in October, a jury found North Chicago-based Abbott and Reckitt’s formula subsidiary Mead Johnson not responsible for a baby developing necrotizing enterocolitis, or NEC, from their cow-milk-based formulas. NEC is a serious, and sometimes deadly, gastrointestinal disease that primarily afflicts premature infants.

Infant formula makers Abbott and Reckitt saw their stocks decline Friday after a judge ruled plaintiffs could pursue a new trial against the companies.

Reckitt said on Friday a U.S. circuit court has ruled that a new trial could be sought by plaintiffs in a case that had accused the London-listed firm and Abbott of failing to warn of the risks of premature baby formulas.

Missouri 22nd Judicial Circuit Court Judge Michael Noble granted the plaintiff's motion for a new trial on Thursday, citing the “widespread misconduct” of defendants Abbott Laboratories Inc. and Mead Johnson.

Reckitt Benckiser is moving forward with the sale of its nutrition operations housing the Mead Johnson infant-formula business.

Abbott Laboratories and Reckitt Benckiser Group Plc shares fell as a judge ordered a new trial after rejecting a verdict that had cleared the companies of liability over claims they hid potential risks of their premature-infant formulas.