Doctors should be more aware of the health risks of a little understood but "not uncommon" practice in which some pregnant women have cravings for nonfood substances, from dirt and laundry starch to tire inner tubes, a National Academy of Sciences committee said yesterday.

In a report to the government on alternative dietary practices and nutritional abuses during pregnancy, the panel said that some pregnant women and their babies are at special risk because of eating practices that may deprive them of needed nutrients and expose them to potentially toxic compounds.

The eight-member group of academic experts cautioned against any use of alcohol or tobacco during pregnancy, recommended "moderation in caffeine intake" and discouraged use of over-the-counter drugs.

But it noted that the so-called "orthodox middle-class American diet" may not be acceptable to many Americans and suggested that diets during pregnancy should be tailored to the special needs of women in ethnic and religious groups.

The report said that health-care professionals "should be alert" to the possible dangers of a compulsion to consume unsuitable substances, a condition known as "pica" that the group said "has yet to receive the attention that it deserves."

The problem, it said, is "not uncommon among pregnant women, particularly among low-income black women of rural southern heritage," as well as other ethnic groups, but few women volunteer such information to their doctors. The problem may cause reduced consumption of needed food and exposure to hazardous chemicals, the report said.

While pica of pregnancy is most commonly reported as consumption of dirt and clay or laundry starch, the committee cited examples of pregnant women who repeatedly ate ice, burnt matches, hair, stone or gravel, charcoal, soot, toilet-bowl air fresheners, cigarette ashes, mothballs, antacid tablets, milk of magnesia, baking soda, coffee grounds and even tire inner tubes.

The Academy's Committee on Nutrition of the Mother and Preschool Child also advised avoiding other, more common hazards:

* Alcohol. The committee called alcohol a "dangerous drug" that may be "one of the most frequently recognizable causes of mental deficiency and developmental delay."

The risks of serious birth defects are strongest among severe chronic alcoholic women. But recent studies show that about 10 percent of women who drink as little as 1 to 2 ounces of alcohol per day during the earliest part of pregnancy produce infants with "recognizable alterations" in growth or development. Limited evidence suggests that some degree of growth and nervous-system impairment may persist later.

The panel concluded that "although infrequent or modest alcohol ingestion may not constitute a hazard to the fetus . . . , a 'safe' level of alcohol intake for pregnant women has not been established," and advising against alcohol would be "prudent."

* Tobacco. Smoking during pregnancy is well-recognized as "one of the most important preventable" causes of low birth weight, it said. Children of women who smoke may have higher rates of disease and death up to 5 years of age. Women also have higher risk of vaginal bleeding and miscarriage.

* Caffeine. This common central nervous system stimulant is found in coffee, tea, cocoa, chocolate, cola and some other soft drinks and drugs.

While animal studies have suggested a risk of birth defects, human evidence of risks to the fetus is "inconclusive" and the "best and most recent study to date suggests that caffeine may pose no significant risks," the committee said. It recommended "moderation in caffeine intake during pregnancy."

The report also urged sensitivity to cultural differences. Traditional dietary guidelines during pregnancy include increased protein and calcium from meat and dairy products. Alternative choices should be offered to those on health, vegetarian or other diets, the panel said.