There is growing evidence that mobile health (mHealth) approaches including short messaging service (SMS) can improve antiretroviral therapy (ART) adherence, but consensus is lacking regarding communication of HIV-related information. Most interventions to date have delivered SMS that do not overtly refer to HIV or ART in order to avoid risk of status disclosure. In formative work for an ongoing randomized controlled trial (RCT) evaluating one-way and two-way educational SMS for prevention of mother-to-child-transmission (PMTCT) adherence in Kenya, we conducted 10 focus group discussions (FGDs) with 87 HIV-infected peripartum women to determine desirability and preferred terminology of HIV-related content. SMS for the RCT were developed based on FGD findings. Roughly half of FGD participants supported receiving SMS containing overtly HIV-related terms, such as ‘HIV’ and ‘medication’, citing desire for detailed educational messages about ART and PMTCT. Those opposed to overt content expressed concerns about confidentiality. Many participants argued that acceptability of HIV-related content depended on the recipient’s disclosure status and others’ access to her phone. Based on these findings, both covert and overt SMS were developed for the RCT and participants who owned their phone or had disclosed their HIV status to anyone with access to their phone were able to choose one of three options: (1) covert SMS only, (2) overt SMS only in response to HIV-related questions from the participant, (3) overt SMS routinely, initiated by the study. Of the 825 participants in the RCT, 94% were eligible to receive overt SMS. Of these, 66% opted to receive routine overt SMS and 10% to receive participant-initiated overt SMS. These findings show there may be interest in overt HIV-related information by SMS when risk of status disclosure is low, and support use of messaging strategies that allows participant choice in HIV-related content while protecting against undesired disclosure.