A structured psychiatric interview will assess current psychiatric syndromes in participants. The Diagnostic Assessment Research Tool (DART) will be conducted at baseline, T2 and T3 to assess change in psychiatric symptoms over the study period.

A structured psychiatric interview will assess current psychiatric syndromes in participants. The Diagnostic Assessment Research Tool (DART) will be conducted at baseline, T2 and T3 to assess change in psychiatric symptoms over the study period.

A reliable and valid 7-item self-report scale that assesses the symptoms of generalized anxiety disorder, the most common comorbidity of PND. A cutoff of ≥10 defines clinically important levels of anxiety symptoms and changes in scores >4 are accepted as being indicative of clinically significant change.

A reliable and valid 7-item self-report scale that assesses the symptoms of generalized anxiety disorder, the most common comorbidity of PND. A cutoff of ≥10 defines clinically important levels of anxiety symptoms and changes in scores >4 are accepted as being indicative of clinically significant change.

The Parenting Stress Index (Short Form) is a 36-item parent self-report measure that identifies potentially dysfunctional parent-child systems on three subscales: parental distress, parent-child dysfunctional interaction, and difficult child. The measure also produces a total score that is an indication of overall level of stress a person is feeling in their role as a parent. Higher scores indicate higher levels of stress.

The Parenting Stress Index (Short Form) is a 36-item parent self-report measure that identifies potentially dysfunctional parent-child systems on three subscales: parental distress, parent-child dysfunctional interaction, and difficult child. The measure also produces a total score that is an indication of overall level of stress a person is feeling in their role as a parent. Higher scores indicate higher levels of stress.

A 12-item scale designed to measure perceived social support from three sources: (1) family, (2) friends and (3) significant other. Items are scored on a 7-point scale, and total scores range from 12-84 with higher scores indicating a higher level of perceived social support. A score of 12-35 indicates low perceived social support, 36-60 indicates medium perceived social support and 61-84 indicates high perceived social support.

A 12-item scale designed to measure perceived social support from three sources: (1) family, (2) friends and (3) significant other. Items are scored on a 7-point scale, and total scores range from 12-84 with higher scores indicating a higher level of perceived social support. A score of 12-35 indicates low perceived social support, 36-60 indicates medium perceived social support and 61-84 indicates high perceived social support.

The Dyadic Adjustment Scale (DAS) will be used to measure an individual's feelings about their relationship with an intimate partner. The scale contains 32-item with items scored on 2-, 5-,6-, or 7-point scales. The DAS contains four subscales: dyadic consensus, dyadic satisfaction, dyadic cohesion, and affective expression. Total scale scores were used in this study, with higher scores indicating greater relationship satisfaction.

The Dyadic Adjustment Scale (DAS) will be used to measure an individual's feelings about their relationship with an intimate partner. The scale contains 32-item with items scored on 2-, 5-,6-, or 7-point scales. The DAS contains four subscales: dyadic consensus, dyadic satisfaction, dyadic cohesion, and affective expression. Total scale scores were used in this study, with higher scores indicating greater relationship satisfaction.

The Postpartum Bonding Questionnaire (PBQ) is a 25-item parent-report measure that assesses four aspects of father-infant relations: (1) bonding, (2) rejection and anger towards the infant, (3) infant-focused anxiety and (4) incipient abuse. Subscales 1-3 will be explored as a continuous outcome using subscale total score. Each item is scored on a scale of 0-5, with higher scores suggestive of more problems. Father-infant bonding will be measured as a continuous and dichotomous outcome, using cut-off scores for each subscale indicating bonding disorders. Cutoff values of 12 for the bonding subscale, 17 for rejection and anger, and 10 for infant-focused anxiety have been proposed to define bonding disorders in each category.

The Postpartum Bonding Questionnaire (PBQ) is a 25-item parent-report measure that assesses four aspects of father-infant relations: (1) bonding, (2) rejection and anger towards the infant, (3) infant-focused anxiety and (4) incipient abuse. Subscales 1-3 will be explored as a continuous outcome using subscale total score. Each item is scored on a scale of 0-5, with higher scores suggestive of more problems. Father-infant bonding will be measured as a continuous and dichotomous outcome, using cut-off scores for each subscale indicating bonding disorders. Cutoff values of 12 for the bonding subscale, 17 for rejection and anger, and 10 for infant-focused anxiety have been proposed to define bonding disorders in each category.

The Infant Behaviour Questionnaire-Revised (Very Short Form) (IBQR) is a parent-report measure of infant temperament. The IBQ-R (Very Short Form) consists of 37 items answered on a 7-point scale (1-7) and assesses 3 factors: Positive Affectivity/Surgency with 13 items, Negative Emotionality with 12 items, and Orienting/Regulatory Capacity with 12 items; higher scores indicate greater alignment with the domain.

The Infant Behaviour Questionnaire-Revised (Very Short Form) (IBQR) is a parent-report measure of infant temperament. The IBQ-R (Very Short Form) consists of 37 items answered on a 7-point scale (1-7) and assesses 3 factors: Positive Affectivity/Surgency with 13 items, Negative Emotionality with 12 items, and Orienting/Regulatory Capacity with 12 items; higher scores indicate greater alignment with the domain.

To assess maternal perinatal depression (PND), partners of fathers participating in the study will complete the EPDS. The EPDS is a 10-item gold standard measure of PND. Total scores range from 0-30 with higher scores indicating worse depressive symptoms. A score of ≥10 is consistent with possible PND, ≥13 is consistent with probable PND and changes in scores >4 are accepted as being indicative of clinically significant change.

To assess maternal perinatal depression (PND), partners of fathers participating in the study will complete the EPDS. The EPDS is a 10-item gold standard measure of PND. Total scores range from 0-30 with higher scores indicating worse depressive symptoms. A score of ≥10 is consistent with possible PND, ≥13 is consistent with probable PND and changes in scores >4 are accepted as being indicative of clinically significant change.

Healthcare resource utilization data will be collected using a questionnaire used in prior work and adapted for the postpartum period (based on the Canadian Community Health Survey and Service Use and Resources Form). Participants will provide information on all healthcare service and medication use from T1 to T3 from the perspective of the public health care payer.

Healthcare resource utilization data will be collected using a questionnaire used in prior work and adapted for the postpartum period (based on the Canadian Community Health Survey and Service Use and Resources Form). Participants will provide information on all healthcare service and medication use from T1 to T3 from the perspective of the public health care payer.

The EQ-5D-5L is a utility-based health-related quality of life instrument assessing five domains (mobility, self-care, usual activities, pain, depression/anxiety) and will be administered at T1-T3. Its validity in measuring the impact of depression is established. We will use its Canadian algorithm to convert responses to health utility. QALYs will be calculated by multiplying the health utility for the corresponding time period (i.e., area under the curve approach).

The EQ-5D-5L is a utility-based health-related quality of life instrument assessing five domains (mobility, self-care, usual activities, pain, depression/anxiety) and will be administered at T1-T3. Its validity in measuring the impact of depression is established. We will use its Canadian algorithm to convert responses to health utility. QALYs will be calculated by multiplying the health utility for the corresponding time period (i.e., area under the curve approach).

Intervention participants only. We will assess participant satisfaction with the intervention using the eight-item Client Satisfaction Questionnaire (CSQ-8). The CSQ-8 consists of eight items assessing the level of satisfaction with the intervention on a 4-point Likert-type scale, as well as one open-ended question. Responses to the open-ended question will be analyzed using content analysis to inform acceptability of the intervention.