The population in the region South-Limburg (NL) suffers from a deprived health status compared to rest of the Netherlands, including unfavorable perinatal health outcomes that impact the child’s health and development in later life. To turn the tide, South-Limburg aims to achieve a ‘promising start to life’ by focusing on the first 1,000 days of life: pregnant women and families with children aged 0-2 years. In particular, the focus is on pregnant women and families in a vulnerable position, facing (a combination of) medical and, especially, social problems (e.g., housing, financial, relational, psychosocial, addiction). Delivering timely and appropriate tailored care and support to this target group requires close cooperation between professionals from the medical domain (i.e., midwife, maternity care, GP), social domain (i.e., social work, municipal support), and public health domain (youth health care). 
 In three low socioeconomic status municipalities in South-Limburg, a co-creation process was started in 2020 to strengthen cross-domain collaboration in delivering timely care and support tailored to the needs of pregnant women and families with children aged 0-2 years in a vulnerable position. Professionals’ input was derived during meetings with stakeholders from the three domains. Input from pregnant women/young families in a vulnerable position was gained through interviews regarding their experiences with current care/support during pregnancy and in the first years of the child’s life. These showed that, among others, they often feel unheard or ignored by professionals; lack of clarity about who is in charge when several professionals are involved; lack of attention for psychosocial problems; insufficient father involvement by professionals.
 As a result of the co-creation process, a case-based multidisciplinary consultation was developed. Essential elements are: professionals from the medical, social, and public health domain join in, as well as the pregnant woman or family involved; professionals use the shared language of ‘Positive Health’ to match the family’s needs and wishes; agreements on referral to care or support are noted in a care plan and the family is assigned a case director.
 The case-based multidisciplinary consultations in the three municipalities started at the beginning of 2022. A practice-based action research is conducted to gain insight into its creation, implementation, functioning, and further development. Research methods include interviews, observations, and questionnaires. First results are available from 24 interviews with professionals involved in the co-creation process about their views on cross-domain collaboration. Themes addressed are among others: importance of early identification of problems; better understanding of other professionals’ expertise; conditions that facilitate or hinder cross-domain collaboration. Results are discussed in the four-yearly meetings per municipality with professionals from the medical, social, and public health domain. Points for action are prioritized and will be monitored over time. Also, client journeys will be conducted to address families’ experiences with the multidisciplinary consultation and referral to care and support.
 This form of cross-domain collaboration, supported by a practice-based action research, can serve as an example for the international audience interested in improving population health by investing in prevention at the very early onset of life.