The purpose of this study is to find the most effective and safe treatment to prevent the passage of HIV from an infected mother to her baby.

1. To assess the effectiveness of the addition of a single dose of nevirapine (NVP) to Zidovudine (ZDV, also known as AZT) as used in the Botswana mother-to-child transmission (MTCT) National Program, in reducing transmission of HIV-1 from mother to child. To determine if maternal NVP (per HIVNET 012 protocol) is necessary in the setting of maternal ZDV from 34 weeks gestation through delivery AND single-dose prophylactic infant NVP at birth plus ZDV from birth to 4 weeks for the reduction of transmission of HIV-1 from mother to child.
2. To assess the effect of prophylactic AZT given to infants during breast feeding on HIV transmission.
3. To confirm the safety and tolerance of one dose of NVP given to mothers and infants
4. To evaluate the safety and tolerance of AZT given to infants for up to 6 months of age
5. To determine the association between assigned infant feeding strategy and maternal morbidity and mortality
6. To determine the rates of virologic response to NNRTI-containing HAART at 26 and 52 weeks after initiating treatment, among HIV+ women who previously received single dose NVP versus placebo during labour.

Inclusion Criteria:

• Mothers must be no more than 34 weeks pregnant, intending to carry to term, intending to stay in area for at least 7 months, and consenting to HIV-1 testing and participation; HIV-1 infected by ELISA confirmed by Western blot; etc.