The Early Life Cohort Feasibility Study, conducted between April 2021 and December 2024, aimed to test the feasibility of sampling and recruitment for a new UK-wide birth cohort study. The study focused on collecting data from a nationally representative sample of UK-born babies in their first year of life, capturing information about their economic and social environments, health, wellbeing, and development. The study was conducted in response to the economic and social changes brought about by the Covid-19 pandemic and Brexit, with a focus on understanding how inequalities in early child development are evolving. The study involved 1,918 families, with data collection through interviews with mothers and fathers, and included innovative measures such as neuro-scientific assessments and biosample collection. The study also tested the feasibility of linking data to electronic and administrative records. The project emphasized engaging traditionally underrepresented populations and included sample boosts for disadvantaged and ethnic minority families. The findings from this feasibility study will inform the design of a main study, which has received funding from the Economic and Social Research Council. The data collected will be made available to the research and policy community, contributing to a better understanding of the challenges facing the new generation of UK-born babies.