This study explores amino acid changes of the reverse transcriptase (rt) of CRF01_AE isolates from pregnant women naive to antiretroviral drugs before and 2, 6, and 52 weeks after exposure to single dose nevirapine (sdNVP). Results based on 51 observations showed that the proportion of isolates with nonnucleoside reverse transcriptase inhibitor (NNRTI) RMs in the group treated with sdNVP (n = 35) increased from 0% pre-NVP to 22.9% at week 2 postpartum (pp) and 22.9% at week 6 pp. In the group treated with zidovudine + sdNVP (n = 16), the proportion with RM was 31.3% and 18.8% at weeks 2 and 6 pp, respectively. Only a few RMs were still detected at week 52 pp. No apparent subtype-specific treatment-related mutations were detected. NNRTI RM occurrence in CRF01_AE strains is similar to subtype A, D, and CRF02_AG strains after exposure to antiretroviral drugs for PMTCT.