Birth defects such as lung abnormalities, cardiovascular problems and chromosome disorders continue to rank as the nation's fifth leading cause of premature loss of life, federal health researchers say.

The national Centers for Disease Control, which tabulates "years of potential life lost" nationwide to determine the role of various conditions in premature mortality, reported Thursday that in 1986, birth defects robbed their victims of 651,523 years of life they would have lived before age 65.That ranked fifth among all causes of premature life-years lost, the Atlanta-based agency said. Ranking first was unintentional injury, resulting in about 2.4 million lost life-years, followed by cancers, heart disease and suicide and homicide.

Birth defects have ranked fifth in all previous studies of premature mortality published as far back as 1984, said researcher David Erickson.

"As infant mortality due to other causes has been reduced (with advances in prenatal care and medical treatment), congenital anomalies (birth defects) have become the leading cause of infant mortality," the CDC said in its weekly report.

In detailed statistics from 1985, the latest year for which such data are available, the leading category of premature mortality from birth defects was lung abnormality - either impartial development or abnormal growth of the lungs. Those conditions accounted for more than 9 percent of the life-years lost to birth defects, the CDC said.

Ranking behind lung abnormalities as a cause of premature loss of life were conditions where infants were born with incomplete brains.