This chapter explores fertility patterns among migrant populations in OECD countries and the limits of the measures commonly used to describe them. It analyses the factors shaping fertility gaps between native‑ and foreign-born women, as well as those driving convergence over time. The chapter also assesses the indirect and direct contribution of migrants to the total number of births in OECD countries and their drivers – namely, the share of migrants in the total population, their age and sex composition, as well as the migration channel through which they arrive. Finally, it points to some of the implications of these trends for population dynamics and the labour market integration among migrants in OECD countries.