Objective: To assess incidence and possible risk factors of severe maternal morbidity and mortality from cardiovascular disease in the Netherlands. Design: A prospective population based cohort study. Setting: All 98 maternity units in the Netherlands. Population: All women delivering in the Netherlands between August 2004 and August 2006 (n = 371,021) Methods: Cases of severe maternal morbidity and mortality from cardiovascular disease were prospectively collected during a two-year period in the Netherlands. Women with cardiovascular complications during pregnancy or postpartum who were admitted to the ward, intensive care or coronary care unit were included. Cardiovascular morbidity was defined as cardiomyopathy, valvular disease, ischaemic heart disease, arrhythmias or aortic dissection. All women delivering in the same period served as a reference cohort. Main outcome measures: Incidence, case fatality rates and possible risk factors. Results: Incidence of severe maternal morbidity due to cardiovascular disease was 2.3 per 10,000 deliveries (84/358,874). Maternal mortality rate from cardiovascular disease was 3.0 per 100,000 deliveries (11/358,874). Case fatality rate in women with severe maternal morbidity due to cardiovascular disease was 13% (11/84). Case fatality rate was highest