A small study found no heart damage in babies whose mothers had been given AZT to keep their infants from getting the AIDS virus.
Several recent studies had suggested that prenatal exposure to zidovudine, marketed as AZT or Retrovir, might damage babies' hearts.
The study by Dr. Steven E. Lipshultz of the University of Rochester was a small one - 48 babies exposed to the drug. He and doctors in Boston, Cleveland, Los Angeles, New York, Houston and Bethesda, Md., checked the babies' hearts every four to six months until they were 5.
The study was reported in Thursday's New England Journal of Medicine.
Without the drug, 25 of every 100 children born to HIV-infected women will be infected with the virus, Dr. Lynne M. Mofenson of the National Institute of Child Health and Human Development wrote in an editorial.
With zidovudine treatment, 23 of these infants will be spared infection, she wrote.
The study was sponsored by the National Heart, Lung & Blood Institute and by the National Institutes of Health.
Until another equally effective medicine is found, the data strongly suggest the benefits outweigh any risk to babies' hearts, said Dr. Claude Lenfant, director of the National Heart, Lung & Blood Institute.