Community health workers (CHWs) will facilitate peer group sessions with mothers and fathers of children aged 0-18 months at enrollment. CHWs will deliver key messages and facilitate problem-solving and skill-building activities to promote nutrition and parenting-related behavior change. The group sessions will last between 1.5-2 hours and groups will meet biweekly for a period of 12 months. Due to the COVID pandemic, group sessions were paused for three months (March-June 2020). The intervention resumed in July 2020 with delivery via home visits rather than peer groups, and concluded in September 2020.

Local standard of care

Nutrition-related social and behavior change (SBC) messages and activities for mothers and fathers focused on infant and young child feeding (IYCF), dietary diversity, water, sanitation, and hygiene (WASH), food access (use of income and home-grown foods), psychosocial well-being, gender equity, intra-household resource allocation, partner communication and household decision-making

Nutrition- and parenting-related social and behavior change (SBC) messages and activities for mothers focused on infant and young child feeding (IYCF), dietary diversity, responsive caregiving and child stimulation (play and communication), water, sanitation, and hygiene (WASH), food access (use of income and home-grown foods), psychosocial well-being, gender equity, intra-household resource allocation, partner communication and household decision-making

Nutrition- and parenting-related social and behavior change (SBC) messages and activities for mothers and fathers focused on infant and young child feeding (IYCF), dietary diversity, responsive caregiving and child stimulation (play and communication), water, sanitation, and hygiene (WASH), food access (use of income and home-grown foods), psychosocial well-being, gender equity, intra-household resource allocation, partner communication and household decision-making

Calculated as height-for-age Z-scores (HAZ) and weight-for-height Z-scores (WHZ), based on WHO Multicentre Child Growth Standards.

Using a caregiver self-reported questionnaire adapted from WHO-UNICEF, proportion of children aged six months or older (breastfeeding and non-breastfeeding) who meet minimum meal frequency guidelines during the previous 24 hours.

Interactions of the child with each parent using the Observation of Mother-Child Interactions tool. Total scores are summed. A higher score represents better parent-child interactions.

Caregiver (mother and father) knowledge of early childhood development (ECD) assessed using a caregiver self-report questionnaire of the perceived expected ages at which children can attain developmental milestones. Responses within a theoretically defined age range are scored as correct, and an overall knowledge of ECD score is created by summing the total number of correct items. Higher scores represent improved knowledge of ECD.

Caregiver (mother and father) knowledge on two topics: 1) Breastfeeding knowledge and support score; 2) Complementary feeding knowledge score (food consistency, nutritious porridge, growth); These are based on questionnaire adapted from WHO-UNICEF. Total scores (# of correct responses) are summed; a higher score represents higher level of knowledge related to recommended IYCF practices.

Consumption of animal source foods (ASF: eggs, meat, and fish but excluding dairy) yesterday by child given father, mother, or child consumed ASF [household ASF consumption] yesterday; Consumption of ASF yesterday by mother given household ASF consumption yesterday; Consumption of ASF yesterday by father given household ASF consumption yesterday

Responsive feeding was measured among mothers using a maternal-reported scale. Each item is scored on 4-point Likert scale: 0 = never, 1 = sometimes, 2 = often, and 3 = always. Negatively worded items were reverse scored. We created an overall responsive feeding score based on the average of 8 items, whereby higher scores indicated more responsive feeding behaviors.

Caregiver (mother and father) stimulation practices assessed using a caregiver self-report questionnaire of the frequency of engagement in stimulation activities (e.g., naming things, playing) with the child in the past week, adapted from the Family Care Indicators. Each item was scored on a 4-point frequency scale (0=never, 1=once or twice a week, 2=multiple times a week, and 3=every day or nearly every day) and summed for a total score. Higher scores represent more frequent engagement in stimulation.

For the brief version of the Co-parenting Relationship Scale (CRS), each item is scored on a 4-point scale, ranging from 0=not true, 1=a little bit true, 2=mostly true, 3=very true. The items are averaged to generate a total score, which similarly ranges from 0 to 3. Higher values of the total average score indicate more positive co-parenting.

Couples' communication and decision-making with respect to household matters (e.g., income, food allocation) using a self-report questionnaire adapted from Promundo and asked to both mothers and fathers. Two sub-scales will be reported: (1) frequency of communication, which is the average across 8 Likert-scored items (3=often, 2=sometimes, 1=rarely, and 0=never); (2) women's decision-making power, which is the total number of decisions over which the woman had the final say independently or jointly with her partner (8 total items). Higher scores will represent more frequent couples' communication and greater women's decision-making power.

Attitudes toward gender norms and roles assessed on both women and men. For each of the 12 items on the scale, women and men will report their level of agreement scored on a 5-point scale ranging from 1 (strongly agree) to 5 (strongly disagree). The items are summarized to generate a total score ranging from 12 to 60 or a standardized z-score. Higher values indicate more gender equitable attitudes toward gender norms and women's and men's social roles and relations within a household.

Time use patterns using 7 day recall, particularly chores and childcare activities, using adapted version of International Food Policy Research Institute's Women's Empowerment in Agriculture (WEIA) tool, assessed on both mothers and fathers. Two main indicators of time use will be reported - time spent on work activities (which can be further grouped into domestic chores and income-generating activities) and non-work activities (leisure and rest) - which each refer to the total number of hours spent for that category of activities. Smaller differences in time spent between men and women indicate greater gender equity at household level.

Using a caregiver self-report questionnaire adapted from WHO-UNICEF, 2 items will be administered to caregivers to calculate proportion of households that purify drinking water.

Using an observational checklist adapted from WHO-UNICEF, 1 item will assess presence of animal feces in house or compound (yes/no).

Using a caregiver self-report questionnaire adapted from WHO-UNICEF, 3 items will be administered to measure change in frequency of handwashing with cleansing agent at critical times during the past 24 hours.

Using a caregiver self-report questionnaire adapted from WHO-UNICEF, 3 items will be administered to measure change in frequency of child handwashing with cleansing agent at critical times during the past 24 hours.

Caregiver (mother and father) knowledge of recommended water, sanitation, and hygiene (WASH) practices (making food safe, avoiding sickness, washing hands). These are based on questionnaire adapted from WHO-UNICEF. Total scores (# of correct responses) are summed; a higher score represents higher level of knowledge related to recommended WASH practices.

Maternal and paternal depressive symptoms will be measured using the Self-Reporting Questionnaire (SRQ-20, excluding the item on suicidal ideation). The SRQ-20 comprises 20 yes/no items to assess the presence of depression and anxiety-related symptoms in the past 30 days. The 19 items used in this study will be summed to create a total score, ranging from 0 to 20.

Mothers' experience of intimate partner violence will be measured based on self-reported experiences of physical, emotional, and/or sexual violence by their male partner in the past 3 months. These questions come from IPV questionnaire in the domestic violence module of the Tanzania Demographic and Health Surveys. Maternal victimization of IPV will be analyzed according to four classifications: (1) any type of violence; (2) any physical violence; (3) any emotional violence; and (4) any sexual violence.

The Parental Distress subscale of the Parenting Stress Index questionnaire was used with both mothers and fathers. Each item is scored on a 4-point Likert scale. Applicable items will be reverse-coded, such that the highest response option=4 is in the direction of more parenting stress and response option=1 is reflective of minimal/no parenting stress. Total scores will be calculated for the Parental Distress subscale. Higher scores indicate greater parenting stress.