BiBBS is an interventional birth cohort study that builds on the Born in Bradford (BiB) birth cohort, aiming to understand the effects of early-life interventions on children's health and development. BiBBS follows families from pregnancy through childhood to evaluate the impact of early-life interventions for children aged 0-3 years in three deprived, ethnically diverse areas of Bradford, England. Recruitment began in 2016, and over 5,600 families were included when recruitment was completed in July 2024. The sample was representative of the pregnant population (61% Pakistani heritage, 12% White British, 8% other South Asian and 6% Central and Eastern European ethnicity) living in the Better Start Bradford areas as of November 2019, with the majority of participants (84%) living in the lowest decile of the Index of Multiple Deprivation, and many living in vulnerable circumstances.