Since 1994, Zidovudine, or AZT, has been the officially recommended therapy for preventing the maternal to child transmission of the human immunodeficiency virus (HIV) throughout the industrialized world, and its use has been associated with a sharp decline in the incidence of AIDS in children. In the U.S., the drop in pediatric AIDS during this period has been more than 60 percent.

However, several recent studies have suggested that the use of AZT to prevent the spread of HIV from mother to child may result in cardiac abnormalities in children. Now new data from an NHLBI pediatric AIDS study provide reassuring evidence that AZT is not associated with any significant negative clinical effects on the heart. These data show no significant differences in cardiac function between children exposed to AZT and those not exposed, regardless of their HIV status.

The data are from the NHLBI's "Pediatric Pulmonary and Cardiovascular Complications of Vertically Transmitted HIV Infection (P2C2) Study." They are published in the paper on "Absence of Cardiac Toxicity of Zidovudine (AZT) in Infants" that appears in the September 14, 2000 issue of the New England Journal of Medicine.

Although observational data suggest that other agents may prevent maternal to child HIV transmission, controlled studies of these agents have not been conducted, and we know little about their safety profiles. One such agent, nevirapine, has been suggested as an effective therapy in countries where pregnant women have limited access to prenatal care and may benefit from a simpler regimen.

Until such time as another agent is identified that can match the record of AZT in preventing maternal to child HIV transmission, the new data strongly suggest that the benefits of using AZT outweigh any possible cardiac risks to the infant, and physicians should continue using this therapy to treat pregnant women with HIV.

NHLBI press releases and other materials are online at www.nhlbi.nih.gov .