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.

Major adaptations occur in the maternal cardiovascular system during normal pregnancy and knowledge of these changes is essential to the management of women with cardiovascular disease. Cardiac output increases during pregnancy but the extent and timing of this increase and the underlying causes have been a subject of debate. The controversy was largely the result of differences in during pregnancy in our department.'0 In our early validatory studies cardiac output was calculated from the pulmonary, mitral, and aortic valves, which allowed us a "within patient" control for the values recorded. We initially validated these results from the aortic, pulmonary, and mitral valves against simultaneous direct Fick measurements. The correlation was good and the limits of agreement were + 0 8 1/min.'0 We also studied within patient, intraobserver, and chronological coefficients of variation for the measurements. These were all equal to or less than 5% for each of the three sites studied. The technique was then applied systematically to several serial studies of cardiac output in pregnant subjects. The results form the basis for the summary of haemodynamic changes that follows.Haemodynamic changes during normal singleton pregnancy Our initial longitudinal studies of cardiac output started before conception and continued through to the postnatal period. Because of the effect on cardiac output of the supine position, which leads to caval occlusion by the gravid uterus,"1 throughout all the studies measurements were performed in the left half lateral position.Cardiac output had increased by five weeks after the last menstrual period and the increase continued to 24 weeks when it was 45% above the non-pregnant level (fig 1). Thereafter no further significant change was found. Both heart rate and stroke volume contributed to this increase: the heart rate increase was seen by five weeks' gestation and continued till 32 weeks. The stroke volume increase occurred a little later at eight weeks and reached its maximum at 540 on 12 May 2018 by guest. Protected by copyright.

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Objective-To examine the results of fetal cardiac scanning and audit the changes in performance resulting from the introduction of a training programme for obstetric ultrasonographers. Methods-Using the database of the Northern Regional Congenital Abnormality Survey (NORCAS), fetuses with complex or significant congenital heart disease (CCHD) diagnosed prenatally in 1994 were identified. A simple programme of centralised and local training was instituted in 1995 by the department of paediatric cardiology to teach obstetric ultrasonographers in district general hospital maternity departments to identify congenital heart malformations. The results of the training programme were assessed by comparing the 1994 identification rate of CCHD with the rates for 1996 and 1997. Results-Birth rate fell during the study from 35 026 in 1994