A 28-year-old Montgomery County woman who was treated last year for infertility gave birth to quintuplets yesterday at George Washington University Hospital in what appears to be the first successful quintuple birth on record in the District of Columbia.

The babies, four boys and a girl, were delivered prematurely by cesarean section between 4:27 and 4:29 a.m. by a 32-member medical team that had monitored and supervised their prenatal progress since January.

All five were reported in excellent condition by Dr. Allan Weingold, chairman of the hospital's department of obstetrics and gynecology.

Also reported doing well was their mother, Pamela Pisner, of Olney, a secretary in the office of the commissioner of the U.S. Food and Drug Administration. She had known she was carrying quints, Weingold said, and had been hospitalized since May 17 in anticipation of the birth.

Weingold said there "may have been" a sixth fetus present in the womb at some time during Pisner's pregnancy that did not survive. He said laboratory tests were being conducted to settle the question.

The quintuplets were the first born in the United States since last Aug. 4 when Amy Chikaraishi gave birth to four girls and a boy at a suburban Chicago hospital.

Historically, Weingold said, quintuplets have occurred only once in every 25 million to 30 million births, with one case anticipated in the United States every 10 or 15 years.

Fertility drugs, however, have dramatically skewed those statistics through their ability to stimulate the endocrine glands that trigger ovulation in women.

"This," Weingold said, "is one of the side effects."

Pisner and her husband Daniel, a management consultant currently unemployed, had hoped for children for most of their eight-year marriage, according to neighbors in Olney.

She, however, had been unable to conceive, and Weingold said she had been under treatment with Pergonal, a drug first compounded in Italy more than 20 years ago and now well-known for its ability to trigger multiple births. Between 20 percent and one-third of all women treated with Pergonal subsequently give birth to more than one infant, Weingold said.

Daniel Pisner, in a statement released by the hospital, thanked the George Washington medical staff for "making this medical miracle possible. Our lives have been enriched beyond measure."

Weingold said the father was present at the birth, the mother was awake, and both wept, "as did a number of people in the room at the time."

Pisner did not attend the news conference because he wanted to be with his wife and wanted her to share any media attention triggered by the event, Weingold said.

"For the next few days we want to get to meet our new family members and give Pam a chance to recover from her surgery. Later this week we will be available to answer press inquiries," the Pisner statement said.

Dr. Maureen C. Edwards, the hospital's director of newborn services, said the quintuplets are being watched for respiratory difficulties but appear "in no apparent danger and should have an uncomplicated course."

She said they ranged in size from 3 pounds, 4 ounces for the first-born boy to 2 pounds, 6 ounces for the girl, who was born third, and were "as well in the delivery room as full- term babies" despite being born nearly eight weeks early.

On a scale of 10 factors by which doctors rate the health of newborn infants, she said, the Pisner quints scored between 9.1 and 9.5.

Several friends and acquaintances described the Pisners as a "very handsome" and "interesting and articulate couple," excited and delighted upon learning last January that quintuplets were on the way.

"They told us all about it," said Mabel Dove, 36, who lives next door to the Pisner's gray, maroon-shuttered, three-story town house on Buehler Court in Olney, and this week is expecting a child of her own.

"We were all out digging our cars out of the snow when he said they'd been trying for years," said Evalena Washington, another Buehler Court neighbor, "and lo and behold what happened."

Wayne Pines, a friend of Mrs. Pisner from work, said the news was "all over FDA" where she continued to work "in good spirits" until she entered the hospital last month.

Weingold described the Pisners as an "extraordinary couple . . . compliant and complacent" within the medical constraints necessitated by her confinement.

Their attitude, he said, was "a great comfort to the staff" and Mrs. Pisner was "a tremendous pleasure to all of us to care for."

Mrs. Pisner had been scheduled to deliver Aug. 13, Weingold said, but delivery was advanced when doctors discovered by ultrasound examination that two of the smaller fetuses were lagging in growth and probably could be given better care outside their mother's womb.

It was moved up still further, he said, when Mrs. Pisner went into premature labor complicated by hypertension. At 3 a.m. yesterday, a decision was made to operate, Weingold said, and within 90 minutes the quints were born.

Weingold said it is currently believed that each of the Pisner infants grew from a separate fertilized egg, meaning that all would be fraternal siblings rather than identical.

A set of identical quintuplets was born to a family named Turner at the District's old Freedmen's Hospital in 1945. All the infants, however, died within moments of birth.

A set of quints born at George Washington Hospital in 1964 after only 19 weeks gestation also died. Like Pamela Pisner, their mother, Linda P. Barnes, had been under treatment with Pergonal, then being tested at the National Institutes of Health.