Myer L, et al. - Because pregnant and postpartum women with HIV frequently exhibit elevated viral load (VL) early after antiretroviral therapy (ART) initiation, researchers examined the relative contributions of pre-ART drug resistance mutations (DRMs) vs nonadherence in the etiology of elevated VL. Within a cohort of women initiating ART during pregnancy in Cape Town, South Africa, women with raised VL after initial suppression incidence-density matched were compared with women who sustained suppression over time. Pre-ART DRMs were reported in 10% of cases and 5% of controls; all mutations were to nonnucleoside reverse transcriptase inhibitors. According to findings, < 10% of all elevated VL in the cohort may be attributable to pre-ART DRMs compared with > 90% attributable to ART nonadherence.