A D.C. Superior Court jury awarded $750,000 yesterday to the family of a 12-year-old girl who was born with birth defects after her mother took Bendectin, the widely used morning sickness medication that has been prescribed for some 33 million women worldwide.

The verdict against Merrell Dow Pharmaceuticals Inc. of Cincinnati, the makers of the drug, was the first major Bendectin judgment against the firm, and the first to find the company negligent in marketing the drug after scientific evidence suggested it might cause a wide range of deformities in fetuses. The case decided yesterday is one of hundreds of lawsuits that have been filed against the company.

"Obviously, we are ecstatic. This is a case that is long overdue. The company is going to have to face up to its responsibilities," said Barry Nace, the lawyer who represented Mary Oxendine of Mitchellville, Md., who was born with a shortened right arm that was missing fingers and parts of the hand.

"We found information in the company's files that they had knowledge of the problems with Bendectin as early as the late 1960s," Nace said in an interview. During the four-week trial, Nace contended that animal studies and human epidemiological data gathered by the drug firm in the 1960s and early 1970s suggested that Bendectin should be studied further "because the results showed there was increased animal deaths and malformations of the fetus."

But the company "never did the studies," he said. The plaintiffs argued during the trial that an initial 1962 study by company research director Dr. Carl Bunde, purporting to show no hazard, was seriously flawed because many of the women studied had not actually received the drug.

Merrill Dow spokesman William R. Donaldson, in an interview yesterday, strongly disputed the plaintiffs' contentions. "The verdict, we feel, is not consistent with the overwhelming weight of scientific evidence that shows Bendectin is not associated with increased risk of birth defects," he said.

Donaldson said the drug has been subjected to at least 20 epidemiological studies, including impartial reviews supervised by the federal Food and Drug Administration. "The vast accumulation of data," he said, showed no hazard. He said the company's 1962 study "was not as sophisticated" as more recent studies, but he said its findings were nonetheless borne out by later analyses.

Bendectin, introduced in 1956 by Richardson-Merrell Co., which is now a division of the Dow Chemical Co., is the only drug approved by FDA for use in treating the nausea and vomiting of early pregnancy. It is also sold widely abroad, sometimes without prescription.

The FDA has found no causal link between the drug and birth defects, but is "continuing to review animal data and human epidemiological studies," FDA spokeswoman Faye Peterson said yesterday. Of at least 13 studies of Bendectin reviewed by FDA, two have suggested that the drug causes heart defects and cleft palate, Peterson said. Those two studies are being repeated in an effort to determine their accuracy, she said.

Since 1980, the FDA has warned women that Bendectin should be taken only for severe nausea and vomiting that cannot be treated without drugs. Pregnant women--especially in the early days of pregnancy when embryos are formed--should instead try to treat the symptoms by "conservative treatments" such as eating dry crackers, drinking very hot or very cold beverages, and resting frequently, FDA said.

Medical experts generally say that nausea will not imperil an embryo, but severe vomiting may. The FDA said the drug should be used only in severe cases, but Bendectin was widely promoted in its early years for nausea sufferers, whose numbers are greater than those women who suffer from both nausea and vomiting.

Yesterday's verdict came after about seven hours of deliberations by the 12-member jury, which had heard a series of expert witnesses for Merrell Dow testify that the studies did not prove the drug is linked to birth defects. But the plaintiffs accused the firm of "manipulating data" and presented two rebuttal witnesses, Nace said.

In addition to the verdict awarding the Oxendines compensatory damages for the birth defects, a second trial is to be held before Superior Court Judge Joseph M. Hannon to consider the plaintiffs' request for more than $1 million in punitive damages against Merrell Dow.

Bendectin is the subject of an estimated 300 lawsuits in state and federal courts, according to plaintiffs and defense figures. In the only other case that has reached trial, a Florida family won a $20,000 judgement in 1980, but yielded no finding of fault by the company.

Mary Oxendine is a sixth grader at Ardmore Elementary School in Prince George's County.

"I think this was a fair verdict on the evidence," said her father, William Oxendine, 42, an engineer with the Department of Energy.

"We have gone through an emotional period. We always thought since she was born that it was caused by something my wife had taken," said Oxendine. His wife, Joan, he said, a nurse-practitioner, always looks up possible side effects before any of the Oxendines take medications, he said.

"She found no side effects listed," he said.