BackgroundIn 2018, the Dutch government initiated the Solid Start program to provide each child with the best start in life. Key program elements are a biopsychosocial perspective on pregnancy and children’s development and stimulating local collaborations between social and health domains, with a specific focus on (future) families in vulnerable situations. Two programs for interprofessional collaboration between maternity and social care professionals to optimize care for pregnant women in vulnerable situations were developed and implemented, in Groningen in 2017 and in South Limburg in 2021. This paper describes the extent of implementation of these programs and the perceptions of involved professionals about determinants that influence program implementation.MethodsWe conducted a mixed-methods study in 2021 and 2022 in two Dutch regions, Groningen and South Limburg. Questionnaires were sent to primary care midwives, hospital-based midwives, obstetricians (i.e. maternity care professionals), (coordinating) youth health care nurses and social workers (i.e. social care professionals), involved in the execution of the programs. Semi-structured interviews were held with involved professionals to enrich the quantitative data. Quantitative and qualitative data were collected and analyzed using Fleuren's implementation model.ResultsThe findings of the questionnaire (n = 60) and interviews (n = 28) indicate that professionals in both regions are generally positive about the implemented programs. However, there was limited knowledge and use of the program in Groningen. Promoting factors for implementation were mentioned on the determinants for the innovation and the user. Maternity care professionals prefer a general, conversational way to identify vulnerabilities that connects to midwives’ daily practice. Low-threshold, personal contact with clear agreements for referral and consultation between professionals contributes to implementation. Professionals agree that properly identifying vulnerabilities and referring women to appropriate care is an important task and contributes to better care. On the determinants of the organization, professionals indicate some preconditions for successful implementation, such as clearly described roles and responsibilities, interprofessional training, time and financial resources.ConclusionsAreas for improvement for the implementation of interprofessional collaboration between maternity care and social care focus mainly on determinants of the organization, which should be addressed both regionally and nationally. In addition, sustainable implementation requires continuous awareness of influencing factors and a process of evaluation, adaptation and support of the target group.