A D.C. Superior Court judge has ordered a new trial in a 1983 case in which a jury awarded $750,000 to a Maryland teen-ager who was born with physical deformities after her mother took the antinausea drug Bendectin during pregnancy.

Judge Peter H. Wolf granted the new trial last week to Merrell Dow Pharmaceuticals Inc., the manufacturer of the drug, in an order stating that "there is a substantial danger that there was an unjust result that can be attributed to {a witness'} false testimony about his credentials."

Barry Nace, who represented Mary Virginia Oxendine, now 17, of Mitchellville, Md., said yesterday that he plans to appeal the decision. Nace charged the decision was "terrible . . . for this little girl" who won the case five years ago before a jury.

Judge Joseph Hannon, who presided over the jury trial, threw out the jury's verdict in 1983, saying the evidence was not sufficient to prove that Bendectin was the cause of the child's birth defects.

A three-judge panel of the D.C. Court of Appeals reinstated the jury verdict. Merrell Dow asked the full Court of Appeals to rehear the appeal, but the court refused.

The company then asked the Supreme Court to order a new trial based on the contention that Oxendine's expert witness testified falsely about his credentials.