This chapter examines key issues related to maternal mental health, particularly depression and anxiety in the perinatal period. Significant numbers of women experience mental health problems in pregnancy and after birth and recognising and responding to the symptoms and experience is important not only for the individual woman but for her baby and family. The chapter addresses the prevalence of maternal mental health problems globally, the risk and protective factors for poor mental health in particular, and the impact of complex social and situation factors in shaping women’s experiences. The chapter concludes by outlining what is known about effective treatments and services including approaches to screening and assessment.