Aims This study aims to evaluate the effectiveness of an innovative postnatal risk assessment (the postnatal Rotterdam Reproductive Risk Reduction checklist: R4U) and corresponding care pathways in Preventive Child Healthcare (PCHC), along with PCHC professional satisfaction. Design Four PCHC organizations located in three municipalities with a higher adverse perinatal outcome than the national average were selected for participation. The study concerns a historically controlled study design. Methods The study enrolled participants from September 2016 until December 2017. The historical cohort existed of children born in previous years from 2008 until 2016. The outcome measure was defined as catch-up growth: more than 0.67 standard deviation score weight for height increase in the first 6 months of life. PCHC professional opinion was assessed with a digital survey. Results After the inclusion period, 1,953 children were included in the intervention cohort and 7,436 children in the historical cohort. Catch-up growth was significantly less common in the intervention cohort; 14.9% versus 19.5% in the historical cohort (p < 0.001). A regression sensitivity analysis, using matching, showed an odds ratio of 0.957 (95% CI 0.938-0.976) for the intervention cohort. In the survey, 74 PCHC physicians and nurses participated; most of them were neutral concerning the benefits of the postnatal R4U. Conclusion This study shows that the implementation of a novel postnatal risk assessment including in PCHC is feasible and effective. Final efforts to ensure a widespread implementation should be taken. Impact PCHC offers a unique opportunity to recognize and address risk factors for growth and development in children and to implement care pathways. Effective and widely implemented risk assessments in antenatal and PCHC are scarce. To our knowledge, this kind of evidence-based postnatal risk assessment has not been implemented in PCHC before and seizes the opportunity to prevent catch-up growth and its long-term effects.