Serial haemodynamic investigations were performed in 15 women at 38 weeks gestation and then 2, 6, 12 and 24 weeks after delivery. Cardiac output was measured by Doppler and cross‐sectional echocardiography at the aortic, pulmonary and mitral valves. Cardiac chamber size and ventricular function were investigated by M‐mode echocardiography. Flow measurements at the three intracardiac sites correlated closely. Cardiac output fell from a mean of 7.421/min at 38 weeks to 4.961/min at 24 weeks after delivery, a fall of 33%. Most of this decrease (28%) had occurred by 2 weeks. This was associated with a 20% reduction in heart rate and an 18% reduction in stroke volume. By 2 weeks after delivery there was a significant decrease in left atrial dimension and left ventricular end‐diastolic dimension. Left ventricular wall thickness and mass declined throughout the period of study as did aortic, pulmonary and mitral valve areas. M‐mode derived indices of myocardial contractility were all significantly reduced by 2 weeks and thereafter showed no further change. No haemodynamic differences were found between lactating and non‐lactating mothers.