To evaluate the safety of rgp120/HIV-1MN vaccine in HIV-1 infected pregnant women with CD4 counts >= 400 cells/mm3. To evaluate the immunogenicity of this vaccine in pregnant women and the passive acquisition of vaccine-specific antibody in their infants. To evaluate the induction or augmentation by rgp120/HIV-1MN vaccine of mucosal immune response in the gastrointestinal and reproductive tracts during pregnancy. To isolate and genetically characterize the HIV-1 present in cervicovaginal fluid specimens of pregnant women and compare it to that present in their peripheral blood mononuclear cells and to that of their infected infants.