About 20 per cent of pregnant women experience antenatal depression (AD), which not only has deleterious effects on the woman and her baby but also increases the risk of developing postpartum depression. Nurses who understand the prevalence, signs and symptoms, and risk factors associated with AD can help to identify it and prevent the sequelae. The signs and symptoms of depression in pregnancy do not differ from depression at at any other time. However, AD may go undiagnosed because of a focus on maternal and fetal well-being and the attribution of complaints to the physical and hormonal changes associated with pregnancy. Risk factors include history of depression, lack of partner, marital difficulties, lack of social support, poverty, family violence, increased life stress, substance abuse, history of previous abortions, unplanned pregnancy, ambivalence toward the pregnancy and anxiety about the fetus. Most of the standard treatments for depression can be used in pregnant women, with the exception of some antidepressant medications. Supportive therapies--exercise, adequate nutrition, adequate sleep, and support from family and friends--are also indicated. Screening of women with known risk factors is crucial, but the authors suggest that the high overall prevalence of depressive symptoms during pregnancy indicates a need for universal screening.