Cardiovascular diseases are a major cause of complications in pregnancy worldwide, and the number of patients who develop cardiac problems during pregnancy is increasing. Peripartum cardiomyopathy (PPCM) is a potentially life-threatening heart disease that emerges towards the end of pregnancy or in the first months postpartum, in previously healthy women. Symptoms and signs of PPCM are similar to those in patients with idiopathic dilated cardiomyopathy. The incidence varies geographically, most likely because of socioeconomic and genetic factors. The syndrome is associated with a high morbidity and mortality, and diagnosis is often delayed. Various mechanisms have been investigated, including the hypothesis that unbalanced peripartum or postpartum oxidative stress triggers the proteolytic cleavage of the nursing hormone prolactin into a potent antiangiogenic, proapoptotic, and proinflammatory 16 kDa fragment. This theory provides the basis for the discovery of disease-specific biomarkers and promising novel therapeutic targets. In this Review, we describe the latest understanding of the epidemiology, pathophysiology, and novel treatment strategies for patients with PPCM.