Serial hemodynamic measurements were performed in 13 women on two occasions before conception and then at monthly intervals throughout pregnancy. Cardiac output (CO) 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. CO increased from a mean of 4.88 l/min before the conception to a maximum of 7.21 l/min at 32 wk, the increase being significant by 5 wk after the last menstrual period. Heart rate and left ventricular performance increased during the first trimester. Heart rate increased further during the second trimester, during which left atrial and left ventricular end-diastolic dimensions increased, suggesting an increase in venous return. Derived values of total peripheral vascular resistance fell during the first 20 wk. These changes were associated with a progressive increase in valve orifice area and left ventricular wall thickness during pregnancy.

Summary Effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) were determined at constant intervals during and after the normal pregnancies in 25 healthy women. Compared with non‐pregnant values, ERPF increased by 80 per cent during early pregnancy but fell significantly from this new level during the third trimester. GFR, however, remained at a level 50 per cent above the non‐pregnant throughout pregnancy. Filtration fraction (GFR/ERPF) was significantly reduced during early pregnancy but rose to a value equivalent to the non‐pregnant during the third trimester. Comparable data of previous workers are re‐interpreted.

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Summary. 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.

Serial measurements ofcardiac output and mean arterial pressure were performed in 15 women during the first stage of labour and at one and 24 hours after delivery. Cardiac output was measured by Doppler and cross sectional echocardiography at the pulmonary valve. Basal cardiac output (between uterine contractions) increased from a prelabour mean of 6-99 V/min to 7-88 V/min at >s8 cm of cervical dilatation as a result of an increase in stroke volume. Over the same period basal mean arterial pressure also increased. During uterine contractions there was a further increase in cardiac output as a result of increases in both stroke volume and heart rate. The increment in cardiac output during contractions became progressively greater as labour advanced. At s8 cm of dilatation cardiac output increased from a basal mean of 7 88 l/min to 10-57 /min during contractions. There were also further increases in mean blood pressure during contractions. One hour after delivery heart rate and cardiac output had returned to prelabour values, though mean arterial pressure and stroke volume remained raised. By 24 hours after delivery all haemodynamic variables had returned to prelabour values.Haemodynamic changes of the magnitude found in this series are of considerable clinical relevance in managing mothers with complicated cardiovascular function.

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Summary. A non‐invasive technique for the measurement of cardiac output in pregnancy by combined cross‐sectional and Doppler echocardiography at three intracardiac sites is described. The validity of the technique for use during pregnancy is reviewed. Comparison with cardiac output determined simultaneously by the direct Pick technique in 15 non‐pregnant subjects showed close agreement for all three measurement sites. Acceptable measurements were obtained from the aortic and pulmonary valves in all pregnant subjects and from the mitral valve in 84% of pregnant subjects. The within‐patient intra‐observer and hour‐to‐hour variabilities of cardiac output in pregnant and non‐pregnant subjects were <5% of the mean for all three valves studied. Flow measurements at each of the three intracardiac sites correlated closely. The advantages and limitations of the technique for use during pregnancy are discussed.