Deaths of babies less than a month old declined by a quarter in the United States the last decade, thanks to advances in the treatment and prevention of dangerous complications and birth defects, the government said Thursday.

Such deaths dropped from six per 1,000 live births in 1090 to 4.5 in 2001, the Centers for Disease Control and Prevention said. Seventy percent of these deaths were in premature babies, according to the CDC.

The CDC cited several possible reasons for the decline, including advances in lung treatments for premature infants, and wider use of folic acid among pregnant women to prevent serious brain and spinal defects.

The mortality rate remained highest among blacks, with 11.5 deaths per 1,000 live births in 1989 and 8.9 per 1,000 in 2001. The CDC said the rate is higher for blacks in part because of they are more likely than other racial or ethnic groups to give birth prematurely.