The terminally ill, Vietnam-born wife of a State Department engineer has been awarded $1.4 million by a federal judge here who found two physicians employed by the department misdiagnosed the woman's cervical cancer.

U.S. District Judge Joyce Hens Green said testimony in a week-long trial last fall showed "persuasively" that the cancer, missed by the doctors during a 1979 examination, later spread to one of the victim's lungs and now threatens her life.

Green's ruling held the physicians failed to give their patient a pap smear that would have allowed early treatment of a cervical tumor and instead prescribed a drug that served to mask the tumor's presence. The award is against the federal government.

"No one challenges the depth of pain and suffering of this young woman who awaits, tragically, the certainty of death, if not imminent, then more likely than not within the next year," Green said in a 21-page opinion signed Friday and made public yesterday.

The woman is Yen L. Snead, 39, whose husband, Jack R. Snead, is a civil engineer for the Agency for International Development, a branch of the State Department.

She was referred to two private gynecologists after complaining of abnormal menstrual bleeding during a required, biennial physical examination at the department.

The physicians, Drs. Joseph Sheffery and the late Thomas Wilson, were under contract at the time to the State Department Health Clinic.

The clinic examines about 5,500 State Department employes and dependents a year and grants medical clearances for overseas assignments.

The Sneads, through their lawyer, declined comment yesterday. "There is a very, very great sadness on their part," said the attorney, Ira S. Saul of Fairfax County. "There is no joy they would want to speak about in winning the lawsuit ."

The federal government has not decided whether it will appeal the verdict, a Justice Department official said. A senior official in the U.S. Attorney's office said the $1.4 million judgment is "a lot of money," but not unprecedented in malpractice lawsuits against the government.

Sheffery and Wilson originally were named as defendants in the Sneads' complaint, but were dropped by Judge Green as being immune from litigation. Sheffery continues to serve as a medical consultant to the department, a spokesman said yesterday.

The Sneads married in Vietnam in 1973 and later were stationed in Yemen and Egypt. Yen Snead first complained of abnormal menstrual bleeding in Cairo in 1978. She was examined at the department's health clinic here while on leave in 1979 and was referred to Sheffery and Wilson, according to Green's opinion.

Snead was cleared for travel and returned to Egypt, but underwent a radical hysterectomy in 1980 at Alexandria Hospital here after the tumor was discovered.

A cancerous spot on her lung was found during an examination in March of last year.

She has undergone repeated chemotherapy and radiation therapy and takes sleeping pills and anti-depressant drugs to combat the emotional distress of her illness, Green said.