CHICAGO (Reuters) - Americans' life spans expanded to an all-time high last year, the nation's infant mortality rate fell to a new low, and U.S. births outnumbered deaths by about the same as in 1996, a report issued Monday said. Life expectancy in the United States reached 76.5 years in 1997, and the nation's infant mortality rate fell to an all-time low of 7.1 deaths per 1,000 live births, the summary report from Johns Hopkins University and the U.S. National Center for Health Statistics said. In 1996, life expectancy was 76.1 years and the infant mortality rate was 7.2 deaths per 1,000 live births. Births outnumbered deaths by 1.6 million last year, translating into a rate of population increase of 5.9 per 1,000 persons, unchanged from 1996 but down from 6.0 per 1,000 in 1995, the report said. Death rates declined for heart disease, liver disease, diabetes, homicide and suicide in 1997, said the report, which appeared in the journal Pediatrics. In addition, AIDS deaths fell 47 percent last year. The U.S. infant mortality rate, which translated into 27,691 infant deaths, was 3 percent lower than in 1996 when 28,237 babies died, but remained higher than the mortality rates of several developed nations, it said. Birth rates for American women 40 years or older continued to increase, while birth rates among teenage mothers declined for the sixth consecutive year, the report said. Among teenagers, homicide and suicide rates declined after increasing in recent years. In the 15 to 19 age group, murders accounted for 18 percent of all deaths, while suicide accounted for 13 percent of deaths -- both down from 1996.