Pregnant women who are currently receiving AZT are randomized at 20-30 weeks of gestation to begin receiving either HIVIG or IVIG every 28 days up to delivery. Within 12 hours after birth, the infant receives an infusion of matching study drug. During labor, all women receive an intravenous loading dose of AZT administered over 1 hour, followed by continuous infusion during the intrapartum period until the umbilical cord is clamped. All infants receive AZT syrup every 6 hours, beginning as soon as oral fluids are tolerated but within 8-12 hours after birth and continuing for 6 weeks. Women are followed until 26 weeks postpartum. Infants are followed at weeks 1, 2, 4, and then every 4 weeks through week 24, every 12 weeks through week 60, at week 78 (18 months), and at week 104 (24 months).