The goal of this clinical trial is to evaluate the effectiveness of a digital psychoeducational intervention, "What Were We Thinking" (WWWT), to prevent the development of postpartum depression and anxiety symptoms in first-time mothers in Chile. The study includes adult women with a healthy, full-term infant younger than two months who are receiving care in primary health centers.

The main questions it aims to answer are:

• Does participation in the WWWT intervention reduce depressive and anxiety symptoms at 3 months after the end of the intervention compared to usual care?
• Does participation in the intervention improve maternal self-efficacy, perceived social support, and coparenting relationship quality compared to usual care? Researchers will compare an experimental group receiving the full WWWT intervention with a control group receiving usual care to determine the effectiveness of the intervention.

Participants will:

• Complete self-report questionnaires assessing depressive symptoms, anxiety symptoms, maternal self-efficacy, perceived social support, and coparenting at baseline and at 3-month follow-up

• Be randomly assigned to either the intervention group or the control group

• Receive the WWWT intervention between 4 and 10 weeks postpartum (intervention group), including:

  • Fourteen psychoeducational video modules (3-5 minutes each) delivered via text messaging over 4-5 weeks
  • Individual contact with a trained facilitator through text messaging
  • One virtual group session with other mothers and a facilitator

• Continue receiving usual care in primary health services (control group) and receive a shortened version of the intervention after the follow-up assessment

Postpartum depression and anxiety are common mental health conditions that affect women during the transition to motherhood and have significant consequences for maternal well-being, parenting, and infant development. In Chile, a substantial proportion of women report elevated depressive and anxiety symptoms during the postpartum period. Despite the implementation of universal screening strategies in primary health care, access to mental health treatment remains limited, as many women identified as at risk do not engage in or receive appropriate care. This gap highlights the need for preventive interventions that can be delivered early and at scale.

Preventive psychosocial interventions targeting modifiable risk factors, such as maternal self-efficacy and perceived social support, have shown effectiveness in reducing the risk of developing postpartum mental health difficulties. However, engagement in face-to-face interventions is often low. In this context, digital health (e-mental health) and mobile health (mHealth) interventions offer a promising alternative, particularly in settings with high mobile phone access and limited mental health resources. Guided digital interventions that include human support have demonstrated higher adherence and effectiveness compared to unguided formats.

"What Were We Thinking" (WWWT) is a psychoeducational, preventive intervention originally developed in Australia to reduce the risk of postpartum depression and anxiety among first-time mothers. The intervention targets key modifiable risk factors, including maternal self-efficacy in infant care and the quality of partner support. The program has been culturally adapted for use in Chile and further adapted to an mHealth format to facilitate delivery through mobile phones.

The Chilean mHealth version of WWWT includes three main components: (1) fourteen brief psychoeducational video modules (3-5 minutes each) delivered via text messaging over a period of 4 to 5 weeks, each accompanied by reflective prompts; (2) asynchronous communication with a trained facilitator through text messaging to provide guidance, answer questions, and support engagement; and (3) one virtual group session with other participating mothers led by the facilitator. The intervention is delivered between 4 and 10 weeks postpartum. Facilitators are trained health professionals (e.g., psychologists, midwives, nurses) with knowledge in perinatal mental health, and they are also responsible for referring participants to primary care services when needed.

A previous feasibility study conducted in Chile demonstrated high acceptability and feasibility of the mHealth WWWT intervention, as well as positive perceptions among participants regarding its usefulness for maternal well-being and partner involvement. Preliminary findings suggested that the intervention may be particularly beneficial for women presenting with mild symptoms at baseline, consistent with its preventive focus. However, no significant differences were found between intervention and control groups in overall symptom levels, possibly due to elevated baseline distress during the COVID-19 pandemic. Therefore, further research is needed to evaluate the effectiveness of the intervention under non-crisis conditions and in a larger sample.

The present study is a randomized controlled trial with two parallel arms (intervention and control) designed to evaluate the effectiveness of the WWWT intervention in preventing postpartum depression and anxiety symptoms. Participants are first-time mothers with infants younger than two months receiving care in primary health centers in Chile. After baseline assessment, participants are randomly assigned (1:1) to either the intervention group, which receives the full WWWT program, or the control group, which receives usual care. Follow-up assessments are conducted 3 months after completion of the intervention.

Primary outcomes include depressive and anxiety symptoms. Secondary outcomes include maternal self-efficacy, perceived social support, and coparenting relationship quality. Outcomes are assessed using validated self-report measures administered online at baseline and follow-up.

This study will provide rigorous evidence on the effectiveness of a scalable, culturally adapted digital preventive intervention for postpartum mental health in a Latin American context. Findings may inform the integration of mHealth interventions into primary health care services and contribute to improving maternal mental health and early child development outcomes.

Inclusion Criteria:

• First-time mothers (primiparous women)
• Aged 18 years or older
• Having a healthy, full-term infant younger than 2 months of age
• Receiving prenatal or postnatal care at participating primary health centers in Chile
• Having access to a mobile phone capable of receiving calls and text messages
• Able to understand and communicate in Spanish

Exclusion Criteria:

• Severe symptoms of depression or anxiety at baseline requiring immediate specialized mental health treatment
• Severe psychosocial problems (e.g., substance abuse, domestic violence, significant cognitive impairment)
• Infant born preterm or with severe medical conditions (e.g., genetic disorders or serious neonatal complications)
• Inability to provide informed consent or participate in study procedures due to language or cognitive barriers

De-identified individual participant data (IPD) will be shared upon reasonable request after publication of the primary study results. Data that may be shared include participant-level outcome data, baseline characteristics, and study-related variables. Identifiable information will be removed to ensure confidentiality. Requests for data access will require approval by the principal investigator and may be subject to a data sharing agreement. Data will be made available for academic research purposes only.