 Unfortunately, NVP-containing regimens are the most widely used regimens for pregnant women in developing countries due to its low cost and its availability in fixed-dose combinations. These study will explore how fast NVP is eliminated from women after delivery and to see if given zidovudinelamivudine AZT3TC for 1 or 2 weeks after NVP discontinuation can help reduce the development of NVP resistant virus. 