AMENDED: Part 2: To determine the safety profile of rCD4-IgG in HIV-1-infected women at the onset of labor and in their newborns. To determine the extent of placental transfer of rCD4-IgG when administered to the mother at onset of labor. To determine the pharmacokinetics of rCD4-IgG in newborns. To obtain preliminary evidence of the ability of rCD4-IgG to prevent intrapartum transmission of HIV-1 from mother to fetus.