When 25-year-old Beatrice Pratt died on the operating table 10 years ago and her relatives sued claiming medical malpractice, they expected a sizable award, not unlike the almost $650,000 they won this week in D.C. Superior Court.

What they hadn't foreseen, however, was that it would be lawyers retained by the family and not Pratt's doctors who would be ordered to pay the $643,493.

A six-member jury found Wednesday that the lawyers that Pratt family members retained to handle their original medical malpractice case, Daniel N. Steven and Marvin D. Waldman, were negligent, causing the suit to be dismissed and depriving Pratt's four children of further rights to recover damages from her doctors.

Steven called the verdict "antilawyer," and said it is "very bad news" for the legal community.

Steven, who said he had won many malpratice cases for his clients, explained that during the discovery process in the Pratt case "we became morally convinced that there was no medical malpractice case here . . . .

"But what this [verdict] means is that lawyers are going to be forced to go forward with medical malpractice cases even if they are only marginal and weak or no case at all . . . because when there is a bad result, like a death, there is always going to be someone somewhere who will testify that there is medical negligence."

"That's just loony tunes," countered Charles Parson, who with his partner William Reback represented the Pratt family in their legal malpractice suit against Steven and Waldman. "What you're seeing is that it's okay for lawyers to pick up the newspaper and read about big verdicts in medical malpractice cases. But what this verdict really tells you is that if you're going to take a case, be prepared to work it up properly or they're going to look to you for mishandling the case."

To win their case against the two lawyers, Pratt's survivors in essence had to win two trials during the five-week proceedings. They had to prove that Pratt's death was the result of doctors' negligence before they could win their legal malpractice claim.

"Our argument was that [Pratt's four] kids were twice victimized," said Parson. "First, they were the victims of medical negligence that snuffed out their mother's life and they were victims of legal malpractice that snuffed out their right of recovery under the law."

Parson said the family could no longer sue the doctors because in April 1979 Pratt's mother, advised by Steven and Waldman, had agreed to accept about $2,000 from the doctors in exchange for dropping the suit. The money covered a $985.88 funeral bill and legal expenses.

Pratt died Nov. 24, 1975, at Columbia Hospital, 12 days after giving birth to her fourth child and several days after experiencing severe pain in her abdomen. A medical examination attributed her death to a blood clot in the lung that occurred during surgery.

The one medical expert testifying for the Pratt family argued during the recent trial that Pratt should have received anticlotting drugs and that failure to follow conventional surgical techniques resulted in a clot breaking off from the pelvic area and traveling to the lungs.

Steven and Waldman produced a string of medical experts, including some of the doctors who treated Pratt and were named in the original suit, who testified that acceptable medical procedures had been followed.

During the trial, attorneys for Pratt's survivors charged that Steven and Waldman had the case 3 1/2 years but were so ill-prepared by the time the trial date approached that they encouraged the family to drop the case and accept the meager settlement. Pratt lawyers charged that Steven and Waldman did not consult an obstetrician or gynecologist for expert advice and instead relied on a doctor who had no speciality in the field.

Steven and Waldman disputed the accusations and presented such widely known lawyers as Kenneth Mundy to defend their handling of the case. The two lawyers argued that they could not find an obstetrician willing to testify that there was medical negligence.

"I am sure there are many doctors who enjoy the prospect that a plaintiff's lawyer who typically sues doctors has now been sued," said Steven, who also said they plan to appeal. "But the tragedy is that we got sued because we felt it would have been wrong to go to trial where we were convinced there was no malpractice."