PROVIDENCE -- A six-member jury in Rhode Island has found the Parke-Davis pharmaceutical company guilty of failing to properly warn a pregnant woman that she might give birth to a defective child because she was taking the anti-epilepsy drug Dilantin.

The jury, after deliberating 11 hours in a case that lasted six weeks, awarded the woman's twin sons compensatory and punitive damages totaling nearly $14 million. The verdict was rendered two weeks ago.

Sandra Keenan of Seekonk, Mass., claimed that she was told by two doctors in 1977 that she could safely use the drug during her pregnancy. In July 1978, she gave birth to twins who had abnormal facial features and did not walk until after their second birthday.

Max Wistow, Keenan's attorney, claimed that the twins suffered from fetal hydantoin syndrome, which has been linked to Dilantin exposure during pregnancy. The condition causes a variety of physical deformities and retardation. Wistow contended that the children are so severely damaged they will never be able to live independently.

Wistow also produced evidence suggesting that Parke-Davis, which began marketing Dilantin in 1938, knew in the late 1960s that the drug carried a risk of birth defects. Even so, he argued, the company was slow to strengthen the warning label.

During the trial, the company argued that its labels were adequate, that it has been difficult to demonstrate that the drug causes birth defects and that the Keenan twins were not suffering from fetal hydantoin syndrome.

The jury disagreed and awarded $4 million in compensatory damages and nearly $10 million in punitive damages.

The American College of Obstetrics and Gynecology estimated in 1985 that 10 percent of the pregnant women taking Dilantin will give birth to a child with serious problems. Another 30 percent, it was estimated, would have babies with less serious defects.