In this chapter, we review how pregnancy and the postnatal period influence the manifestations of psychiatric disorder. Although rare, the postpartum psychoses can be devastating illnesses, occasionally associated with suicide and require timely treatments to bring them under control. Postnatal depression by contrast is a common and readily diagnosed disorder and responds well to standard treatments such as CBT and medication. However, it may have complex effects on mothering and the new-born in the early months following childbirth, and the present-day perinatal services that manage the bulk of these cases are reviewed here. Any psychiatric disorder can appear during pregnancy, and some conditions may worsen, but a few may paradoxically improve. The prescribing of medication to this population is a complicated task because of teratogenic risks – some known, others imagined – as well their safety in breast feeding, which is also reviewed. Effects on infants and children are important, so the chapter ends with a review of child abuse and neglect and its current diagnosis and management.