In perinatal mental illness not only does the patient suffer, but obstetric outcomes, mother-baby interactions and hence longer term emotional and cognitive development of the child are also affected. Perinatal mental illness also has an impact on other family members. The UK Confidential Enquiry into Maternal and Child Health has consistently found psychiatric disorders to be one of the leading causes of maternal death, often through suicide. Postnatal depression and puerperal psychosis are two disorders most commonly associated with the perinatal period: the first, because of its high prevalence, 13% in the first few months following birth, the second because of its potentially disastrous consequences, including suicide, neglect of the baby and infanticide. [With external links to the current evidence base]