WASHINGTON (AP) -- More and more low-birthweight babies are being born across the country, and the rate is growing even faster in the suburbs than in the cities.

Typically, people living in the nation's central cities are more likely to experience problems with their health than their suburban counterparts, but those differences are narrowing in some cases, according to a report that compares the 100 largest cities with their suburbs.

The report, released Tuesday by researchers at the State University of New York Downstate Medical Center, looked at the change in health measures in both cities and their suburbs between 1990 and 1999 or 2000, depending on availability of data.

For all but low birthweight babies, the statistics improved over the decade - nationally, in cities and in suburbs. The rates of tuberculosis, AIDS, syphilis, gonorrhea and homicide all fell, though some were starting to rise again in the late 1990s.

In the case of low birthweight babies, the problem is still more acute in the central cities than in suburban areas, the report found.

In 1999, 8.9 percent of city babies were born dangerously small - lighter than 5.5 pounds or lighter, making them more likely to be sickly and more likely to die than larger babies. In 1999, 7.0 percent of suburban babies were born that small.

But the differences have narrowed since 1990, when 8.5 percent of city babies and 6.1 percent of suburban babies were born little. The rate of low birthweight babies grew by 14 percent in the suburbs, vs. just 5 percent in the cities.

Nationally, experts say the increase in low birthweight babies is due to a number of factors. More tiny babies who once died at birth are now living; when they died, they were not counted in the low birthweight statistics. More women are using fertility drugs, which leads to more twins, triplets and higher-order multiples, and these babies are more likely to be small. And more older women are having children; their babies also tend to be small.

All of these trends may be more pronounced in the suburbs, said Dennis Andrulis, the report's lead author. At the same time, more lower-income families are moving to the suburbs, and bringing their health risks with them, he said. It's possible, he said, that suburban hospitals are not prepared to deal with these patients' risks as well as the city hospitals are.

"You need to get people into prenatal care, smoking cessation classes," he said. "The system (in the suburbs) is not as prepared to care for vulnerable populations."

Overall, the health differences within communities were greatest in the Northeast and the Midwest, with the central cities much worse off than their neighboring suburbs. But in the West, the differences were narrowing on a host of factors, the report found.

That's particularly true for infant mortality and homicide rates, where there are only narrow differences in the West. For infant mortality, in fact, the rates are higher in the Western suburbs.

"Who would predict that?" Andrulis asked. "The cities and suburbs are beginning to look a lot like each other."

Copyright 2002 The Associated Press. All rights reserved.