A Cincinnati federal court jury yesterday found that Bendectin, a drug used by an estimated 33 million pregnant women from 1957 to 1983 to relieve "morning sickness," did not cause birth defects in children.

The six-member jury deliberated 4 1/2 hours before reaching its verdict in a case brought by about 1,100 people nationwide -- two-thirds of all pending cases against the drug's manufacturer, Merrell Dow Pharmaceuticals.

The plaintiffs argued that the drug caused congenital deformities in babies, but the company said that such defects also occur when women do not take the drug and that the defects could not be traced to the drug.

The verdict is a major victory for a company in a product liability suit. The Bendectin suits, like those involving asbestos and the herbicide Agent Orange, have become increasingly common in recent years.

The Cincinnati case almost never came to trial. Lawyers for both sides agreed last year to a $120 million settlement of all claims against Merrell Dow. Some plaintiffs' lawyers objected to the settlement and the 6th U.S. Circuit Court of Appeals in Cincinnati in effect voided the agreement.

A Merrell Dow spokesman called yesterday's verdict a "very significant win," not only because it may relieve the company of hundreds of millions of dollars in potential damages, but because it may dissuade others from pursuing suits against the company.

"This is the third win in three trials for Merrell Dow," company spokesman William Donaldson said. "The signals are going out that there is no valid claim the drug causes birth defects."

Donaldson said the verdict made it unlikely that the company would try to settle any of the pending lawsuits. "I could never conceive of that at this point," he said.

More lawsuits could be filed in addition to the cases still pending, he said, since the statute of limitations on such suits is 18 years.

The company, which began manufacturing the drug in 1957, took it off the market in June 1983 for what it called "compelling nonmedical reasons," particularly increased costs of litigation and insurance premiums. It has consistently denied that the drug caused birth defects.

Jerry Skinner, an attorney for the plaintiffs, said he would ask the trial judge, Carl B. Rubin, to set aside the verdict or to order a new trial. Such requests, though routine, are usually denied.

If Rubin denied the requests, Skinner said, he would ask the federal appeals court in Cincinnati to overturn the verdict, reached by the jury of five women and one man after five weeks of complex and often conflicting scientific testimony.

Skinner said that the appeal would focus on the two-phase trial procedure Rubin used. In the first phase the jury was to determine whether Bendectin caused birth defects. In the second phase, obviated by yesterday's verdict, the jury would have determined whether Merrell Dow was liable for damages. Skinner said the two-phased approach altered the plaintiffs' presentation and hurt their chances.

Skinner agreed that the verdict, if it stands, could deter other product liability lawyers from filing suit.

Donaldson said the first suit involving Bendectin was filed in Florida in 1977, 20 years after the drug went on the market. The company won that case after two trials.

A D.C. Superior Court jury in 1983 awarded $750,000 in damages to the family of a 12-year-old girl who was born with serious deformities of the right arm and hand after her mother took Bendectin. A judge overruled that verdict.