NEW YORK (Reuters Health) - After a dramatic leap in survival rates for very low birth weight babies up to 1997, there has been little change in survival or health for these infants since then, a new study shows.

"We have made great progress, but over the past few years we're just inching up whereas we were taking bigger steps," Dr. Avroy A. Fanaroff of Rainbow Babies & Children's Hospital in Cleveland, Ohio, told Reuters Health. "We've really consolidated but we haven't taken the next major step forward."

In order for the next big leap to occur, he added, advances in preventing premature birth or a major breakthrough in helping the smallest infants survive must occur, neither of which he expects to happen soon. Nevertheless, according to Fanaroff, increasing use of state-of-the-art care for low birthweight babies will continue to improve survival gradually across the board.

Fanaroff and his colleagues looked at data on infants born weighing 501 grams to 1,500 grams (between 1 pound 2 ounces and 3 pounds 5 ounces) between 1990 and 2002 at 16 US centers.

Between 1997 and 2002, the researchers found, survival rates were 55% for babies weighing 501-750 g; 88% for 751-1,000 g infants; 94% for 1,001-1,250 g; and 96% for 1,251-1,500 g.

About 70% of all very low birthweight infants survived without serious illness.

Between 1990 and 2002, the researchers found, use of steroids before an infant's birth to help mature lungs and prevent bleeding in the brain rose from 20% to 79%. Use of antibiotics for mothers before delivery or during labor rose from 31% to 70% during the same time period.

These approaches, along with efforts to prolong gestation with drugs that decrease uterine contractions, have produced real benefits in survival and health for very small infants, Fanaroff noted. Other advances include improved nutrition and better infection control, he added.

The real measure of outcome for very low birth weight infants will be their long-term neurodevelopmental health, he and his colleagues note, for which data is still being collected.

Most encouragingly, Fanaroff said, the newest group of very small infants to reach school age are faring quite well. At 6 to 8 years of age, he said, "they're looking a lot better than they even looked when they were 2 years old."