Psychiatric disorders occur both during pregnancy and postpartum. The consequences of inadequate treatment in these periods can be dramatic, not only for the mother but also for the infant. The reference books and textbooks used in Norway provide very scanty information on the treatment of psychiatric disorders during pregnancy and postpartum. The use of drugs is a particularly difficult issue, as detrimental effects may arise in the fetus and in the suckling infant.This article is based upon a review of relevant literature supplemented by our own experience in the field.In general, the effect is better documented for drug treatment than for other therapeutic modalities. Some drugs can be used without particular problems during pregnancy and lactation while others have potentially detrimental effects. Often the risk of not giving the mother adequate treatment must be weighed against the potential risks of drug exposure to the infant. Pregnancy-related psychiatric illness would, when recognized, in most cases have a favourable prognosis provided that adequate treatment is given.