Common mental health disorders affect around one in five women during pregnancy and the first year following childbirth. Depression and anxiety disorders are the most prevalent mental health disorders during this period as they are at other times of life. It is important to distinguish postnatal depression from baby blues, which is common and requires no treatment, although it is a potential risk factor for postnatal depression. Postpartum psychosis affects 1 in 1,000 women and can develop very quickly in the first two weeks postpartum, often requiring urgent admission to a specialised mother and baby unit. One in six women with bipolar disorder will develop postpartum psychosis.