Effects of the Parents of Little Ones® - Baby Version® on Parenting Stress and Mindful Parenting in Postpartum Mothers (PdP-B)

Participants allocated to this arm will receive access to Parents of Little Ones® - Baby Version®, a self-guided online parenting program consisting of eight sessions, preferably completed over eight weeks. The program integrates cognitive-behavioral, mindfulness, self-compassion, and mindful parenting strategies. Sessions include psychoeducational videos, interactive exercises, guided practices, and activities to apply the learned strategies in everyday parenting. Participants will complete online questionnaires at baseline, post-intervention (up to week 10), and three-month follow-up (up to week 22).

Parents of Little Ones® - Baby Version® is a self-guided online preventive parenting program designed for mothers during the first 12 months postpartum. The program integrates cognitive-behavioral strategies, mindfulness, self-compassion, acceptance-based approaches, attachment theory, and mindful parenting principles.

The intervention consists of eight online sessions, each lasting approximately 45 minutes, preferably completed at a weekly pace over eight weeks. Sessions include psychoeducational videos, interactive exercises, guided mindfulness and self-compassion practices, and activities designed to help participants apply the strategies in everyday parenting situations.

Participants access the program independently through an online platform, without therapist guidance. The program aims to reduce parenting stress, promote mindful parenting, strengthen maternal psychological resources, and support positive mother-infant interactions.

Participants assigned to the waitlist control group will not receive access to the Parents of Little Ones® - Baby Version® program during the study period. They will continue their usual activities and complete online questionnaires at baseline, post-intervention (up to week 10), and three-month follow-up (up to week 22), following the same assessment schedule as the intervention group.

Changes in parenting stress will be assessed through Parental Stress Scale (PSS). The questionnaire assesses the distress associated with the parental role and has 18 items (e.g., "Caring for my child(ren) sometimes takes more time and energy than I have to give") answered on a five-point Likert scale that ranges from 1 (strongly disagree) to 5 (strongly agree). The total score is calculated as the sum of the items, with higher scores indicating higher levels of parenting stress.

Changes in mindful parenting will be measured by the Interpersonal Mindfulness in Parenting Scale - Infant version (IM-P-I), an adapted version of the Portuguese version of the Interpersonal Mindfulness in Parenting Scale for parents of infants. This version consists of 28 items (e.g., "I tend to criticize myself for not being the kind of parent I want to be") rated on a five-point Likert scale from 1 (never true) to 5 (always true). The scale assesses five mindful parenting dimensions: Listening with Full Attention, Emotional Awareness of the Child, Compassion for the Child, Self-Regulation in Parenting, and Nonjudgmental Acceptance of Parental Functioning. The total score, representing a global measure of mindful parenting, is calculated by summing all the item responses, with higher scores indicating higher levels of mindful parenting.

The presence of depressive symptomatology will be assessed through the Edinburgh Postnatal Depression Scale (EPDS). The EPDS is a 10-item screening tool designed to measure the presence of depressive symptoms (e.g., sadness, tearfulness) in the previous seven days (e.g., "I have been able to laugh and see the funny side of things"). Items are answered in a four-point Likert scale (from 0 to 3). The total score is calculated by summing all item responses, with higher scores indicating greater levels of depressive symptoms. The EPDS total scores will be interpreted using the following severity ranges: none or minimal depression (0-6), mild depression (7-13), moderate depression (14-18), and severe depression (19-30).

Changes in anxiety will be assessed through the Postpartum Specific Anxiety Scale - Research Short Form (PSAS-RSF). The PSAS-RSF is a 16-item self-report questionnaire derived from the original 51-item PSAS to assess specific anxieties related to the postpartum period. As in the original scale, items are divided into four factors: (1) Maternal Competence and Attachment Anxieties; (2) Infant Safety and Welfare Anxieties; (3) Practical Infant Care Anxieties; and (4) Psychosocial Adjustment to Motherhood. Mothers should answer each item considering how they felt in the last seven days, using a four-point Likert scale ranging from 1 (never) to 4 (almost always). The total and subscale scores consist of the sum of the items, with higher scores indicating higher levels of postpartum specific anxiety.

The Maternal Confidence Questionnaire (MCQ) will be used to measure changes in maternal confidence. The MCQ is an instrument that measures a mother's perceived competence in caring for her infant and understanding their needs. It has 13 items (e.g., "I know what makes my baby happy") answered using a five-point Likert scale, ranging from 1 (never) to 5 (always) with higher scores indicating higher maternal perceived competence.

The mother-infant bonding will be assessed by the Postpartum Bonding Questionnaire (PBQ). The PBQ is a self-report questionnaire designed to provide an early indication of mother-infant bonding disorders. It has 12 items (e.g., "I feel distant from my baby") to be rated on a six-point Likert scale, ranging between 0 (never) and 5 (always). The total score is calculated as the sum of the items, with higher scores indicating more impaired mother-infant bonding.

The Perceptions of Coparenting Partners Questionnaire (PCPQ) will be used to assess changes in the coparenting relationship. PCPQ is a self-report questionnaire designed to assess parents' perceptions of the quality of their coparenting relationship. The questionnaire includes 14 items that assess supportive coparenting behaviors (e.g., "My partner and I use similar parenting strategies") and non-supportive coparenting behaviors (e.g., "My partner uses parenting strategies that I asked him or her not to use"). Items are rated on a five-point Likert scale ranging from 1 (never) to 5 (always), and the total score is obtained by calculating the average of all item scores after reversing the scores for non-supportive coparenting behaviors. A higher total score indicates a greater level of supportive coparenting.

Changes in baby social-emotional and behavioral development will be assessed by the Baby Pediatric Symptom Checklist (BPSC). The BPSC is a caregiver-reported screening tool designed to identify difficulties in infants. The measure includes 12 items organized into three domains: Irritability, Inflexibility, and Difficulty with Routines. Each domain comprises four items rated on a three-point scale from 0 (not at all) to 2 (very much). The instrument is intended to facilitate the early detection of potential social and emotional concerns in very young children, supporting timely follow-up when needed. A score of 3 or higher on any subscale suggests that the child may be at risk and warrants further evaluation or clinical attention.

Levels of dispositional mindfulness will be measured by the Mindful Attention Awareness Scale (MAAS). The MAAS comprises 15 items (e.g., "I find it difficult to stay focused on what is happening in the present moment"), rated on a six-point Likert scale ranging from 1 (Almost always) to 6 (Almost never). This instrument assesses an unidimensional construct, reflecting aspects related to a receptive state of mind in which attention is guided by an aware sensitivity to present-moment experiences, involving the simple observation of ongoing events as they unfold. A total scale score may be obtained by summing all items, with higher scores indicating greater levels of dispositional mindfulness.

The Self-Compassion Scale - Short Form (SCS-SF) will be used to assess parents' levels of self-compassion. This scale includes 12 items (e.g., "I try to be understanding and patient toward those aspects of my personality I don't like") that are rated on a five-point Likert scale, from 1 (almost never) to 5 (almost always). The overall score is calculated as the mean of the items, with higher scores reflecting greater self-compassion.

The Parental Reflective Functioning Questionnaire (PRFQ) will be used to assess parents' levels of reflective functioning. The PRFQ is a multidimensional self-report measure consisting of 18 items scored on a seven-point Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree). The instrument includes three subscales: (a) Pre-Mentalizing Modes of Mental States, with higher scores indicating greater difficulty with understanding and interpreting a child's mental experience; (b) Certainty about Mental States, with higher scores reflecting more certainty about what a child is thinking, feeling, or intends to do; and (c) Interest and Curiosity in Mental States, with higher scores reflecting a higher level of parents' interest in their children's inner experiences.

Participants' resource utilization will be assessed retrospectively through a Resource Use Questionnaire developed by the research team based on previously published instruments. The questionnaire will collect information regarding resource utilization for both participants and their children, including healthcare utilization (e.g., emergency department visits, outpatient appointments, hospitalizations, and medication use), absenteeism and presenteeism related to paid and unpaid work among caregivers, and out-of-pocket expenses.

Program feasibility will be evaluated using indicators of adherence, engagement, and attrition. Adherence will be assessed based on the number of sessions completed and the proportion of participants who complete the intervention. Intervention completers will be defined as participants who complete at least 75% of the program. Engagement with the intervention will be examined using platform usage data. Intervention attrition will be assessed based on the proportion of participants who fail to meet the intervention completion criterion within 10 weeks of randomization and will therefore be considered intervention dropouts.

Intervention acceptability will be assessed using study-specific items developed by the research team to capture participants' experiences and perceptions of the program. At the end of the intervention, participants will complete a Final Evaluation Form assessing overall satisfaction with the program, perceived usefulness and impact on parenting, and willingness to recommend the program to others. The form will also assess the usability of the online platform (e.g., ease of use and navigation, clarity of instructions, and comfort using the platform), perceived fit of the intervention with participants' daily routines, perceptions of the intervention format (e.g., session length and overall program duration), and perceived adequacy of contact with the research team. Open-ended questions will invite participants to identify the aspects of the program they found most and least helpful and to provide suggestions for improvement.