With improved maternal medical care and fertility treatments, an increasing proportion of women with congenital cardiac disease and acquired heart disease are becoming pregnant and delivering safely [1]. However, pregnancy has a profound effect on the cardiovascular system, and many conditions are associated with a significant risk of foetal and maternal morbidity and mortality. It has been reported that 0.2–۰٫۴% of all pregnancies are complicated by cardiovascular disease [2], and although death is rare, cardiovascular disease is the biggest indirect cause of maternal death worldwide, with an attributable rate of two deaths per 100,000 [3] in the UK and a similar rate in other countries [4, 5]. The epidemiology of cardiovascular disease in pregnancy varies significantly depending the location of the mother, with much variation in disease rates and processes. Worldwide, hypertensive disease in pregnancy is by far the most prevalent cardiovascular disorder, complicating 2–۸% of all pregnancies in the Western world, predominantly in Latin America and the Caribbean, where it causes one-quarter of all maternal deaths [6]. Rheumatic heart disease is common in developing countries but are now rare in the Western world [7]. A similar variation is observed in peripartum cardiomyopathy (PPCM), with a rising incidence in Western society, estimated most recently at 1:2229 [8], but an estimated rate of 1:1000 in Africa and 1:300 in Haiti [6]. An exact prevalence of women with congenital cardiac disorders who are pregnant is difficult to estimate largely due to the methodology involved in the reported studies, but in the USA nine per 10,000 delivery hospitalisations were for women with congenital heart disease [9]. In most Western countries, most women seen in cardiac–obstetric services have congenital heart disease. Death is rare, but when it does occur it is most often due to myocardial infarction (often coronary dissection), ascending aortic dissection, cardiomyopathy and sudden adult cardiac death [10]. The first area addressed in this review is the physiology of the cardiovascular system during pregnancy. In this section we focus on the key changes that cardiologists need to be aware of. This article does not contain any new studies with human or animal subjects performed by any of the authors.