Longitudinal cohort studies have significant potential to inform policy across a range of child and family areas, including early childhood education and care. Here we describe the relationship between policy-makers and New Zealand's contemporary pre-birth cohort study. We outline a model for policy interaction that highlights the relationship between Growing Up and policy across study design, implementation and analysis. We then describe key policy-relevant questions in the early childhood education and care area that Growing Up has addressed when children were age 2. We used parent-report data for 6242 children to consider: whether socio-economic factors and ethnicity are related to the type, amount and quality of care children receive, and changes in this care across the early years; whether families are intending to utilise '20 Hours ECE' when their children reach age 3, and if not, why not; and whether differences in intentions to use '20 Hours ECE' are based on socio-economic factors, ethnicity and the type of childcare children are receiving at age 2. Results indicated clear differences in nonparental care at age 2 as a function of maternal ethnicity, income, area deprivation and household structure. Several child care proxy quality indicators were lower for children of Maori, Pacific and Asian mothers compared with children of European mothers, and for children living in higher deprivation areas. While 88 % of mothers were intending to utilise the Government's '20 Hours ECE' funding, Asian and Pacific mothers and mothers whose children were cared for by family members were less likely. These findings highlight the importance of continued policy efforts to reduce socio-economic and ethnic disparities in education and care during the preschool years. (author abstract)