LOS ANGELES — In the 25-year history of AIDS, there have been many advances but few victories. Prevention of infections and deaths among young children is one.

The number of children diagnosed with AIDS continues to plummet, even as the overall number of new AIDS cases in the United States remains at more than 40,000 a year.

In 2003, 59 children younger than 13 nationally were diagnosed with AIDS, according to the Centers for Disease Control and Prevention. That's down from 952 cases in 1992, officials said.

Health officials attribute the decline to routine testing of pregnant women and the use of anti-retroviral drugs, such as AZT, during pregnancy and childbirth.

A 1994 study found that one-quarter of pregnant HIV-positive women in the United States passed the virus to their babies when they did not take AZT.

Subsequent studies found the risk could be lowered to less than 2 percent when mothers received prenatal care, took a combination of anti-viral drugs during pregnancy and labor, and allowed their infants to be given AZT in their first six weeks.