Premature and low birth weight infants face increased odds of dying early in life if they are not born in hospitals specially equipped to care for serious newborn illnesses, according to a new study.

Since the 1960s, guidelines have recommended that very low-birth-weight infants be born at highly specialized hospitals, most commonly called level III hospitals. Despite these recommendations, some regions continue to have large percentages of these infants born in lower-level hospitals, the researchers say. Level II hospitals are equipped to care for moderately ill babies and level I hospitals can only provide basic care.

"Although they represent less than 2 percent of U.S. births, 55 percent of infant deaths occur among [very low-birth-weight] infants," the researchers say. Strengthening systems in which states designate specific hospitals to care for these very low-birth-weight or premature infants could save thousands of lives each year, they say.

Sarah Marie Lasswell, of the Centers for Disease Control and Prevention in Atlanta, and colleagues reviewed 41 previous studies to examine the relationship between hospital level at birth and risk of death for very low-birth-weight (3.3 pounds or less) and very premature (32 weeks or less gestation time) infants. Normal gestation time is around 40 weeks and the average baby born in the United States weighs about 7.5 pounds.

The studies on very low-birth-weight babies included a total of 104,944 infants. These infants had a 62 percent increased chance of dying before they were four weeks old or before they were discharged from the hospital if they were born in level I or level II hospital as opposed to a level III hospital.

Extremely low-birth-weight infants, those weighing 2.2 pounds (1000 grams) or less, had an estimated 80 percent increased chance of dying if they were born in a level I or level II hospital.

The studies on premature babies included 9,300 infants. These newborns had a 55 percent increased chance of dying if they weren't born in a level III hospital.

The results are published in the September 1 issue of the Journal of the American Medical Association.