The Breastfeeding - a Good Start Together intervention study aims to increase the proportion of women who breastfeed for four and six months, and proportionately more in a group of women who are in risk of early breastfeeding cessation; and thus reduce social inequality of mother and infant health.

Breastfeeding has numerous health benefits for both mothers and children, and the World Health Organization recommends exclusive breastfeeding for six months. Still, only 12 % of mothers in Denmark breastfeed exclusively at six months postpartum and breastfeeding is subject to significant social inequality. Mothers of young age (below 25 years) and with low educational attainment (not exceeding primary school or vocational) breastfeed for a shorter duration of time than their counterparts. Thus, this group is in high risk of early breastfeeding cessation and is hereafter termed 'the high-risk group'.

The Breastfeeding - a Good Start Together intervention consists of theory based breastfeeding support, supported by printed materials and a web-page providing support and knowledge for families when health visitors are off work, and an intensified intervention aimed at the high-risk group, comprising close follow-up by telephone and an extra home visit. In total, the high-risk group will receive seven telephone calls during week two post partum and 15 weeks post partum, with the highest intensity in the first month (contact once a week), gradually decreasing as the child grows older (contact every second week during the second month, and every third week during the third and fourth month).

Hypothesis: Improving the relationship between health visitors and new families, drawing on tailoring of the communication, which ensures that breastfeeding support matches the needs of the family, will enhance trust and therefore the likelihood of families reaching out to the health nurse when breastfeeding problems occur and thus improving chances of successful breastfeeding in a longer duration of time. Moreover, the theory based breastfeeding support will make the support more easily attainable for families, independent of their sociodemographic background. Improving chances of a successful breastfeeding will improve mother and infant health, the latter especially with regards to lower infant morbidity related to nutrition.

The intervention is a complex intervention, designed as a cluster-randomized trial. Twenty-one municipalities situated in the North Denmark Region and Region of Southern Denmark participate in the study, and according to the number of births among inhabitants these have been randomized to either intervention or control group; 11 intervention municipalities and 10 control municipalities. Basing the randomization on number of births proved to successfully account for other factors, such as rural or urban areas and proportion of high-risk individuals.

The intervention will be implemented from March 2022-December 2023, with data collection commencing April 2022. Health visitors in the intervention municipalities will receive training before delivering the new breastfeeding counselling to the families. The training is expected to reach 225 health visitors in the intervention municipalities and 6000 families of whom 30-40% are in the high-risk group. After the trial period, health visitors in the control municipalities will receive the same training.

The primary outcome measures of the intervention is breastfeeding duration and proxies for infant morbidity related to nutrition. Secondary outcomes are the families' perception of their relationship with the health visitor and parents' action competence and self-efficacy related to breastfeeding.

The primary and secondary outcome measures, are studied in a survey study using electronic questionnaires distributed to mothers recruited through the health-visiting programme at three time-points, and to fathers/partners at one time-point. Further, the effectiveness of the intervention will be analysed using register-data. A difference-in-difference design is applied to measure changes in primary outcomes from before to after the intervention period in both intervention sites and control sites.

The overall target group of the intervention study is all new families accepting the health visiting program with a specific high-risk group of families with mothers of young age or who have low educational attainment. Outcomes of the trial will be analysed for the total population and for the sub-group.

For sample size calculation an estimation of 8 clusters in the intervention arm and 8 clusters in the control arm were used, as this calculation was made prior to successfully recruiting a total of 21 clusters to the trial. The investigators expect a participation of 80% with an attrition of 30%. The ambition is to improve the breastfeeding duration in the intervention clusters to the national level, corresponding to an OR 1.32. With an interclass correlation coefficient of 0.001, a strength of 80% and a 5% significance level can be reached if data are collected from 111 mothers in each cluster, including 52 mothers from the high-risk group in each cluster.

All effectiveness analyses will be using an intention-to-treat approach and will account for the clustering of individuals and potential confounding in a controlled mixed effect regression.

The implementation of the intervention will be analysed in a process evaluation using qualitative and quantitative data. A realist evaluation using qualitative data will explore the mechanisms of change in the intervention, and will highlight what works for whom, under what circumstances.

Further, a health economic evaluation will be performed as a cost-effectiveness analysis where health benefits are measured as changes in the proportion of women breastfeeding at four months post partum, and as a cost-utility analysis where health benefits are measured as gained Quality Adjusted Life-Years (QALYs). Moreover, an analysis of the costs of the intervention related to the costs (and possible savings) in the health system surrounding the intervention sites.

Inclusion Criteria:

1a. Families discharged <72 hours post partum (from 26 April 2022 - 17 January 2023)

1b. Families discharged < 7 days post partum (from 18 January 2023 onwards due to lower than expected recruitment rate)

2. Families with intention of breastfeeding

Exclusion Criteria:

• Insufficient skills in Danish or English language to be able to answer questionnaires and understand interventions conveyed in Danish or English
• Families with mothers with known substance abuse or addiction
• Families expecting more than one child
• Families having delivered preterm, prior to 37 weeks of gestation
• Families with mothers or child having difficulty breastfeeding due to a known morbidity or disablement