Between 1970 and 1983, 519 pregnancies in 405 women with heart disease were managed at the Royal Maternity Hospital, Belfast, Northern Ireland, a rate of 1.3 per 100 deliveries. In 312 (60%) the heart disease was of rheumatic origin, in 161 (31%) congenital, and the remaining 46 (9%) were a miscellaneous group that included arrhythmias, ischaemic heart disease and cardiomyopathies. The New York Heart Association (NHYA) grading was no greater than 1-2 in 445 (86%) pregnancies antenatally. Three maternal deaths occurred, all in the group whose antenatal NYHA grade was 3-4. Heart failure was present in 96 (18%) pregnancies antenatally, and six others developed failure during labour or in the puerperium. Prophylactic antibiotics were not used routinely and infective endocarditis did not occur. The perinatal mortality rate was 19/1000, and the rate of congenital malformations was not raised in the reviewed group.