Becoming a mother is a life-changing event that many experience as a time of joy and affection. However, it can also be a period of great vulnerability and uncertainty with the potential to hinder the mother's well-being and bonding with the baby, and undermine the child's later emotional, social, and cognitive development. The mothers' emotional regulation skills, namely self-compassion, may be useful in protecting the mother and the mother-baby bonding, making them a valuable target of intervention during the perinatal period and a potential protective factor for mental health. Although compassion-based interventions (CBIs) have been proven effective in promoting well-being and reducing mental health difficulties across diverse populations, including the perinatal period, evidence of their impact on maternal well-being and the mother-baby bond remains limited. Thus, the research team propose to explore the acceptability, feasibility, and preliminary efficacy of a CBI during pregnancy on mothers' compassion abilities, and consequent impact on well-being and quality of mother-baby bonding at postpartum.

This pilot cluster randomised trial addresses the research question of 'Does the Care4mommies intervention work to promote mothers' compassion and higher quality of the mother-baby bonding?' Participants will be mothers enrolled in group birth preparation courses (i.e., TAU); those groups will be randomly allocated to Care4mommies plus TAU or TAU only and assessed at pre-intervention and post-intervention(prepartum), and 3-month follow-up(postpartum). At pre- and postintervention, participants will be asked to provide self-reported information on self-compassion, shame and guilt about caring, maternal-fetal attachment, fear of self-compassion, self-criticism, and mental health. At post-intervention, they will also be asked to appraise data collection procedures and the implementation feasibility of the Care4mommies; at follow-up, they will be asked to report on their bonding to their baby. Researchers expect that participants in the Care4mommies plus TAU condition will report significant gains at post-intervention and sustain them until follow-up, both in relation to the mother and in mother-baby bonding, compared to the TAU group. Also it is expected that changes in self-compassion-related variables will explain changes in mother-fetal attachment and postpartum mother-infant bonding.

Developing universal mental health promotion actions in the perinatal period is of paramount importance as the transition to motherhood involves multiple challenges that can hinder women's mental health and well-being. Within the perinatal period, self-compassion seems to be a potentially modifiable cognitive and emotional protective factor that could be a target of interventions contributing to mothers' psychological adjustment and responsiveness towards the baby. Still, Compassion-based Interventions (CBIs) in this period remain scarce. Thus, the current project aims to explore the acceptability, feasibility, and preliminary efficacy of a CBI during pregnancy on mothers' compassion abilities, and the consequent impact on well-being and quality of mother-baby bonding at postpartum. Feasibility studies are a key component of the iterative process for intervention development. It allows for the assessment of practicality, helps to identify challenges, and resource availability, assesses participant recruitment and retention, ensuring the success and ethical conduct of research endeavours. Ultimately, the outcomes of these studies inform the design of a fully powered randomized controlled trial.

This study goal (i.e., 'Does the Care4mommies intervention work to promote mothers' compassion and higher quality of the mother-baby bonding?') will be accomplished using a pilot cluster randomised trial methodology as defined by the CONSORT. Participants will be recruited from public healthcare facilities within an established partnership with ACES Alto Ave. Inclusion criteria will be women aged between 18 to 49 years old (i.e., fertile age), between 26 to 33 weeks into a single-fetus pregnancy, and fluent in Portuguese; otherwise, exclusion criteria will be currently attending another psychological intervention to prevent potential adverse effects from different theoretical approaches to mental health. These participants will be organised into clusters, which will refer to groups attending birth preparation courses as organised by ACES Alto Ave. Those clusters will be randomly assigned to one of two conditions in a 1:1 ratio by a senior member of the research team, not involved in the implementation of the intervention. The conditions are Care4mommies plus TAU (i.e., birth preparation courses) or TAU only. Based on the information provided by ACES Alto Ave, the expected initial sample is 12 clusters, with between 6 and 8 participants. So, 6 experimental groups and 6 control groups will be conducted, for a total of between 36 and 48 participants in each condition.

Participants in both conditions will be asked to fill in a self-report protocol at comparable times: (T1) one week before the intervention starts, (T2) one week after the intervention has ended, and (T3) three months after the intervention has ended (at postpartum). This protocol will address both primary and secondary outcome variables via self-report questionnaires that have previously been appraised for their psychometric properties using Portuguese adult samples. Primary outcomes will be self-compassion, shame and guilt about caring, and mother-infant bonding. Secondary outcomes will be fear of self-compassion, self-criticism, and mental health. All primary and secondary outcomes will be assessed at the three time-points, except for mother-infant bonding, which will be applicable only at T3. Other self-report measures will be used to control potential confounding variables: depressive symptoms, mother's attachment styles, and maternal-fetal attachment at T1, as well as mothers' perspectives of their baby's temperament at T3. Our primary goal will be to assess change in participants over time across conditions; changes are expected only in the Care4mommies plus TAU condition. As a secondary goal, it will be explored if changes in self-compassion-related variables are significant fixed effects of change in mother-fetal attachment and on postpartum mother-infant bonding.

Researchers expect mothers' self-compassion, mental health, and bonding to their baby will increase from pre- to post-intervention and be sustained in the follow-up period only in the experimental group, whereas shame and guilt about caring, fear of self-compassion, and self-criticism are expected to decrease from pre- to post-intervention and at follow-up.

Data analyses will be based on general linear models considering time, condition, and the time with condition interaction as fixed effects; mothers' depressive symptoms, mothers' attachment style, maternal-fetal attachment, and mothers' perception of the baby's temperament will be taken as random effects, as well as any demographic variables that significantly differ between conditions at pre-intervention. Incidence rate ratios (IRR) and confidence intervals (CI), as well as Intraclass correlation coefficient (ICC), marginal coefficient of determination (marginal R2), and conditional coefficient of determination (conditional R2) will be considered when assessing the model's quality, and level of adjustment. Whenever significant fixed effects are found, differences will be further explored via post-hoc analyses.

Findings from this research will have immediate and noteworthy implications. First, this work will gather evidence on which to tailor an intervention to a specific group and to be delivered within specific ecological contexts where it may be easily and freely accessed by that group. Secondly, this work will gather evidence on the efficacy of that tailored intervention in promoting mental health and the quality of mother-infant bonding. Tailored interventions that are developed jointly with the communities that may come to use them and that have a proven impact are more likely to become institutionalised and an integral part of the offer of a given context. Ultimately, this work may result in diversified offers within healthcare facilities that better address the needs of users in a more comprehensive and integrated manner. To further allow this, a final seminar will be held, and scientific papers will be presented to present the projects' results to a wider community and scientific audience. Moreover, results will also be disseminated to community members (i.e., mothers), academics, and practitioners via the website of the project (https://projetocare4mommie.wixsite.com/care4mommies).

Inclusion Criteria:

• being between 26 and 33 weeks into a single-fetus pregnancy,
• being fluent in Portuguese

Exclusion Criteria:

• currently receiving another psychological intervention

Pregnant women

The research fellow who will perform the data analysis of the intervention outcome(s) will be blinded to participants' group allocation.