This is a comparative clinical trial among HIV-infected women and their infants to determine:

1. the benefit of nutritional supplementation given to women during breastfeeding
2. the benefit and safety of antiretroviral (ARV) medications given either to infants or to their mothers to prevent HIV transmission during breastfeeding
3. the feasibility of exclusive breastfeeding followed by early, rapid breastfeeding cessation

This study addresses the complex issues of HIV related maternal morbidity, mortality, and postnatal HIV transmission during breastfeeding and weaning in resource-poor countries. Objectives include assessment of mortality and morbidity among HIV-infected women; evaluation of interventions to reduce HIV transmission to infants exposed by breast milk; and assessment of early weaning as a risk-reduction strategy for infants of HIV-infected mothers.

The study will evaluate the following:

1. The efficacy of a high-density caloric/micronutrient nutritional supplement given to HIV-infected women who breastfeed in preventing maternal depletion (weight loss and micronutrient status).
2. The safety and efficacy of maternal or infant antiretroviral regimens, taken for up to 6 months during breastfeeding, in reducing infant HIV infection rates at 48 weeks.
3. The feasibility of exclusive breastfeeding for 6 months followed by rapid weaning.

Additional study objectives are to evaluate the feasibility of delivering these interventions in resource poor settings and to identify maternal, infant, and virologic factors associated with HIV transmission during breastfeeding.

Inclusion Criteria:

Recruitment and primary eligibility criteria:

• Age > 14 years.
• Ability to give informed assent or consent.
• Evidence of HIV infection, as documented by 2 positive ELISA antibody tests; or 1 positive ELISA, and 1 Western Blot; or 2 separate concurrent rapid tests.
• Currently pregnant (with a single or multiple fetuses).
• Gestation < 30 weeks at referral from 'Call to Action' Program
• No serious current complications of pregnancy.
• Intention to breastfeed.
• Intention to deliver at the institution at which the study is based.
• Not previously enrolled in this study for an earlier pregnancy.
• Other than HIV, no active serious infection, such as tuberculosis or other potentially serious illnesses.
• No previous use of antiretrovirals including the HIVNET 012 regimen.
• Mother's CD4 count > 250 cells/uL determined in the antenatal clinic.
• Mother's ALT < 2.5 x ULN (upper limit of normal) determined in the antenatal clinic

Secondary eligibility criteria and treatment assignment:

• Mother who delivers outside of the institution at which the study is based must present with her infant to the study site within 36 hours of delivery.
• Mother accepts nevirapine and zidovudine+lamivudine 7-day regimen for herself and her infant.
• Infant birth weight > 2000 g.
• No severe congenital malformations or other condition(s) not compatible with life.
• Based on clinical assessment, no maternal condition which would preclude the start of the study intervention.