CD4 counts increase during the postpartum period and may not correctly identify HAART-eligible HIV-positive women. HAART eligibility when defined by two CD4 cutoffs (<200 and <350 cells/microl) measured at two time points (within 96 h of delivery and 6 weeks) in postpartum HIV-positive women was compared. Among HIV-positive women who had CD4 at delivery and 6 weeks (n = 423), time to Stage 3 or 4 opportunistic infection or death was compared using Cox regression between three groups of women: (1) CD4 <200 cells/microl at delivery and 6 weeks, (2) CD4 <200 cells/microl at delivery but >or=200 cells/microl at 6 weeks, and (3) CD4 >or=200 cells/microl at delivery and at 6 weeks. The analysis was repeated using the CD4 <350 cells/microl cut-off. CD4 counts increased by a median (IQR) of 70 (1-178) cells/microl between delivery and 6 weeks and decreased thereafter to approximately delivery levels at 12 months. Only 60% and 61% who had CD4 <200 cells/microl and CD4 <350 cells/microl, respectively, at delivery also had those levels at 6 weeks. Among those with CD4 <350 cells/microl at both delivery and 6 weeks, the risk of death or Stage 3 or 4 disease was 5.27 (95% CI 1.85-14.96) times higher than those with CD4 <350 at delivery but >or=350 cells/microl at 6 weeks. The use of CD4 counts immediately postpartum to define HAART eligibility may lead to substantial misclassification.