Prenatal depression presents a burden and potential risks for the expecting women (Chung et al., 2001; Kim et al. 2013) and may have long-term consequences for the child regarding their cognitive, behavioural, and emotional development (Madigan et al., 2018; Rogers et al., 2020). However, there is a lack of large-scale studies investigating the relationship between prenatal maternal depression and child behavioural and emotional development that control for a common set of relevant potential confounding variables. In this project, we aim to study the effects of prenatal maternal depression on children’s long-term behavioural development and mental health, leveraging large-scale, multi-cohort data in the EU Child Cohort Network. As a secondary objective, we plan to disentangle the effects of pre-pregnancy, prenatal and postnatal depression on offspring development. The strength that comes with studying this research question in the LifeCycle cohort is the large amount of harmonised, multi-cohort data available, which allows us to investigate offspring outcomes over time while also controlling for relevant confounding factors. Furthermore, rather than focusing on a single behavioural outcome, our approach will be comprehensive in that it will examine a range of measures including cognition, internalising and externalising behaviour, and autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). This can aid our understanding of symptom profiles for children prenatally exposed to maternal depression.