A majority of the nation's obstetricians and gynecologists -- almost 78 percent -- have been sued for malpractice at least once in their careers, a new national study shows.

That figure has risen nearly 10 percent since 1987 and is now at an all-time high, said officials of the American College of Obstetricians and Gynecologists (ACOG). The average ob-gyn has been sued three times.

The statistics do not mean "that 78 percent (of ob-gyns) are bad docs, though we are the first to admit there are bad doctors," ACOG president-elect Richard Schwarz said recently. "I think that there is probably an increasing awareness on the part of patients that this is the way you can gain some compensation."

The survey of members of the nation's largest society for ob-gyns found that obstetricians were increasingly sued for stillborn babies and the deaths of newborns, and that the number of suits over brain-damaged newborns remained high. A significant number of gynecology suits involve claims that doctors failed to diagnose cancer, most often breast cancer.

Malpractice suits now take an average of five years to resolve; nearly 40 percent are dropped or settled without any payment to patients. When cases go to arbitration or a court decision, doctors win nearly 69 percent of the time.

What this shows is that "many cases . . . are without merit," said Schwarz, a physician and official at the State University of New York Health Science Center in Brooklyn. "A baby may be born with damage that isn't necessarily the result of liability . . . but it's costly to care for those neurologically damaged infants, and the only recourse those patients have at this juncture is the court system," he said.

By 1989, the new study reported, 25 percent of doctors said they had decreased high-risk deliveries and 12 percent said they had stopped practicing obstetrics entirely.

The study, conducted by Opinion Research Corp. of Washington, also found:

The number of doctors who have been sued more than once is up sharply. Nearly one quarter -- 23.4 percent -- reported four or more malpractice claims by 1989, the study said, compared with 13.5 percent in 1987.

The average payout in all malpractice cases settled in or out of court was $211,320, an increase over the $140,606 reported in 1987. The average amount paid to the plaintiffs in obstetrical malpractice cases was $311,378, compared with $221,379 in 1987. Obstetrical claims involving brain damage or other major injuries to infants averaged $600,000. .