AGAIN AND AGAIN, it happens in the District: a pregnant woman comes into a hospital and is left unattended; the baby is born in a hospital hallway or emergency room instead of the delivery room. At one District hospital, most deliveries are done by residents who are learning how to deliver babies and who know little or nothing about problem births. A doctor tells a story of one premature baby, weighing under two pounds, who was left to die because the attending doctor did not think the child could live. Two hours later, the baby was still alive. The doctor then tried to get the child to breathe regularly -- but the doctor did not know how. The baby was sent to the Children's Hospital National Medical Center in an unheated ambulance. Shortly thereafter, the baby died.

The District ranks first in the country in infant mortality. Two reasons usually given have been the large number of poor people with nutrition problems and the high rate of teen-age pregnancies. But now a report by Mayor Barry's commission on infant mortality says that teen-age pregnancy and malnutrition are not significant factors in the city's infant mortality rate. The major problem, according to the report by a group of doctors from around the nation, is the poor quality of care given pregnant women in city hospitals. Those findings are in line with a draft report prepared by the National Center for Disease Control. That study said the failure to follow medical procedures for premature infants contributed to the death of 40 percent of the babies who died in the District in 1976. The latest report urges that standards be set for the care of pregnant women -- in particular, for those with high-risk pregnancies -- at city hospitals.

Alberto Russo, director of the city's Department of Human Resources, says steps are now being taken to set minimum standards that would be enforced through licensing requirements for hospitals. One change would be to require that hospitals have sufficient skilled staff at all times to handle problem pregnancies. In addition, Mr. Russo said, the mayor's panel has started a campaign to alert pregnant women to the need for prenatal care. Money has also been provided for additional nurses and nutritionists in the city clinics, and a phone number has been established for pregnant women to call for emergency care and advice.

As a list, efforts look substantial. But in the face of an alarming number of infants dying at birth here, they look meager. The mortality rate in the District has remained high for the last two years despite efforts to reduce it. And a change in the licensing procedure could take much too long.

There are examples in other cities of successful efforts to limit infant deaths. In Boston, neighborhood health clinics work closely with hospitals to prevent delivery difficulties. Boston City Hospital has a special program for high-risk pregnant women, such as alcoholics. And its intensive-care nursery staff includes some doctors who specialize in care for newborns. Washington hospitals generally do not have such programs.

There is still another aspect of the District's infant mortality rate: the city has three times the national average of premature births, and no one seems to know why. It could be partly because of bad health in the city generally, especially among the poor, or because of the city's high rate of veneral disease -- second in the nation (to San Francisco).

There is also a problem of "substandard care" of premature babies in hospitals. It has been isolated as one definite cause of the high infant mortality rate. Immediate action by DHR and the mayor's panel on infant mortality -- including pressure for better hospital staffs and higher standards of care for pregnant women -- is not too much to ask.