Arm 1 receives NVP once a week, Arm 2 receives NVP twice a week, and Arm 3 receives NVP daily. There is no placebo control group. The first 18 infants enrolled in each arm will contribute pre- and post- NVP dose blood samples for pharmacokinetics. The remaining infants will contribute data on safety and pre-dose NVP levels only. Infants return to the clinic weekly for visual assessment of NVP toxicity. Women are counseled to stop breast-feeding their infants by the end of 6 months. Infants receive their last dose of NVP at either 24 weeks of age or 1 week after breast-feeding cessation, whichever occurs first, and have follow-up visits until the infant is 32 weeks old.