<jats:p> Introduction: “m-What Were We Thinking” (m-WWWT) is an m-health, intervention oriented to prevent symptoms of postpartum depression and anxiety in first-time mothers. Mothers receive psychoeducation and socioemotional support through written communication via text-messaging (i.e., WhatsApp) with the program counsellor. Although the use of m-health interventions targeting mental health has increased, the form/style of communication through text messages between participants and program counsellors has been understudied. Objective: The aim was to describe the formal structure of the communication (Basic Forms) and the communicational intentions (Communicative Intentions) used in the messages sent by the counsellor and to determine if these are related to the post-intervention outcomes. Methods: 438 text messages sent by the counsellor to 53 first-time mothers (M = 25.32 years, SD = 4.23) who participated in the m-WWWT intervention were analyzed. The Therapeutic Activity Coding System was used to capture the communication as a “Communicative Action”. Results: The study highlighted the counsellor's frequent use of the “assertion” communicative form (82%) and attuned communicative intentions (52%) and explored (39%) in her messages. The attractors of communication were “assert to attune” and “assert to explore”, indicating an empathetic and informative communication style. With respect to their relationship with the intervention outcome, only “assert to explore” messages were positively related to maternal self-efficacy increases. The number of messages was not associated with participants’ characteristics at baseline, except for educational level. Discussion: Our results show the relevance of combining the delivery of information with a communication style that allows the counsellor to connect with the specific needs and emotional tone of the participants. </jats:p>
