Updates headline and lead to include Abbott, updates with comment from Abbott and plaintiff's attorney

By Dietrich Knauth

March 14 (Reuters) - A Missouri judge has ordered Abbott Laboratories ABT.N and Reckitt Benckiser RKT.L 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, re-opening a case that had resulted in a victory for the defendants.

The Thursday ruling comes months after a St. Louis, Missouri state court found that the companies were not responsible for a young boy's debilitating intestinal disease. The case had been a victory for the two companies following large losses in similar trials that had rattled investors.

Missouri Circuit Judge Michael Noble in St. Louis, Missouri, said the defendants’ lawyers had engaged in misconduct that resulted in an unfair verdict from the jury and ordered a new trial.

Abbott and Reckitt said they would appeal.

Abbott spokesperson Scott Stoffel said the jury had reached the correct decision, based on evidence from scientists and governmental regulators who have said there is no conclusive link between preterm infant formula and the plaintiff's son's intestinal disease.

"We are disappointed by the court’s extraordinary decision to set aside the jury’s work," Stoffel said.

"This decision is at complete odds with the law and the facts, and we will appeal," Reckitt said in a statement Friday.

Shares in Reckitt were down 2.8%, and those in Abbott fell 2.9% at 1440 GMT.

Noble said Abbott and Mead Johnson's lawyers intentionally and repeatedly violated clear instructions when presenting evidence to the jury. The defense attorneys "flooded the zone" with objections, presented evidence that the judge had previously disallowed, and confused the jury by attacking "straw man" arguments and saying that babies would "starve to death" if the products were pulled from the market, according to Noble's ruling.

One of Abbott’s lawyers was sanctioned at one point during the trial, and he was not allowed to present evidence or make arguments during the latter half of the five-week trial.

"The misconduct in this case was appalling, and we certainly felt it led to an unfair trial and unjust result for our client," said attorney Tim Cronin, who represented the plaintiff, a young boy named Kaine Whitfield, and his mother.

At the five-week trial in St. Louis, Missouri state court, lawyers for plaintiff Kaine Whitfield had urged jurors to award more than $6.2 billion.

The case is one of about 1,000 similar lawsuits around the country, which have raised alarm from doctors who say the litigation could threaten the formulas' availability or affect medical decisions.

The lawsuit alleged that the companies failed to warn that their specialized formulas used by newborn intensive care units in hospitals could cause necrotizing enterocolitis.

It is a disease that almost exclusively affects premature infants and has an estimated mortality rate of more than 20%.

(Reporting by Aby Jose Koilparambil in Bengaluru and Dietrich Knauth in New York; Editing by Anil D'Silva, Shinjini Ganguli, Alexia Garamfalvi and Diane Craft)

((abyjose.koilparambil@thomsonreuters.com;))