The incidence of fetal alcohol syndrome (FAS), a cluster of birth defects affecting babies born to women who drink heavily during pregnancy, may be seriously underestimated, a new study suggests. And infants who could benefit from early intervention are not getting it because they are not being identified, one of the study's authors said.

Researchers at the University of Texas Southwestern Medical Center in Dallas examined the records of 40 babies born between 1977 and 1980 to 38 known female alcohol abusers. They found symptoms indicating possible FAS in the infants' charts in more than half of the babies, but "there was a 100 percent failure by hospital staff to diagnose the syndrome," the study said.

The researchers followed up on some of the babies studied and found more than half suffered from developmental delays and mental retardation. The researchers said they were unable to complete the study because of a lack of funds.

Although some symptoms of FAS are hard to detect in infants, according to Bertis B. Little, chief author of the study published in the American Journal of Diseases of Children, it should be considered among infants whose mothers' obstetrical records show a history of alcohol abuse.

Little, a clinical geneticist, said the findings indicate that "this is probably a fairly common occurrence in babies born to alcohol abusers, and what we've seen here is that it is common not to even suspect it."

FAS and the somewhat milder FAE -- fetal alcohol effect -- can cause mild to profound retardation, developmental and behavioral problems. It is believed to affect one in about 750 babies born annually in the United States.

While it is difficult to diagnose FAS or FAE in infants, certain physical characteristics are suggestive. These include flattened nasal bridge, narrow forehead, short upturned nose and a head circumference smaller than chest. Some infants lack creases on the palms of their hands. This is caused, Little said, when the infant is drunk, and the sedated fetus fails to move its hands.

Children with developmental problems can be helped by special educational techniques. But, Little said, "you have to recognize the problems early."