Pre-eclampsia is not a uniformly high-resistance, volume-contracted state as previously thought.1 Earlier studies, using direct haemodynamic measurements in women with severe pre-eclampsia requiring invasive monitoring, have described variations in haemodynamic characteristics ranging from a hyperdynamic state with a higher-than-normal cardiac output (CO) and increased left ventricular function to a vasoconstrictive state with decreased CO and diminished left ventricular function. These studies also document variable systemic resistance profiles, ranging from normal- to high-resistance states.2–4 However, since the introduction and evaluation of the Doppler technique for maternal cardiac function in pregnancy,5,6 a series of echocardiographic studies have confirmed the existence of apparent haemodynamic subgroups in women with overt or preclinical pre-eclampsia.7–9 These studies have advocated a maternal hyperdynamic circulation7,9 that is preceding the clinically overt disease9 and may also be present to a variable degree during the more severe stages.7 Furthermore, in one study the effect of maternal haemodynamics on fetal growth in hypertensive pregnancies have been investigated.10 Easterling et al. observed that high-resistance hypertension was associated with lower percentile weights for gestational age, while high CO and low-resistance hypertension were associated with normal fetal growth.10 However, the cardiac investigations in their study were performed in women who were clinically hypertensive.
In previous studies on pre-eclampsia, the influence of the variable characteristics in the maternal central and peripheral haemodynamics on the sensitivity of screening tests or the efficacy of treatment has been masked by the analysis of all pre-eclampsia cases as a single disease entity. However, there is emerging epidemiological evidence to suggest that preterm pre-eclampsia (before 37 weeks) and term pre-eclampsia associated with low-birthweight infants (between 37 and 42 weeks) are likely to share similar disease origins, while term pre-eclampsia may also be associated with large or normal for gestational age fetuses and may thus represent a different subgroup of women.11 Additionally, there is evidence of disparity in screening for pre-eclampsia with uterine artery Dopplers either in the first12 or in the second trimester13 since it has been shown that there is a remarkably higher sensitivity in women with pre-eclampsia complicated by small-for-gestational-age (SGA) babies compared with uncomplicated pre-eclampsia or SGA alone. Furthermore, nondistinction of these varied haemodynamic states may, in part, be why studies utilising volume-loading in severe pre-eclampsia have shown no clear maternal nor fetal benefit.14,15 However, although maternal cardiac function might play an important role in screening and treatment for pre-eclampsia, there is no information to date regarding the degree of changes in the first trimester of pregnancy, presumably because previous investigators were concentrating at the later stages of the disease when it would be more applicable for screening and treatment. Furthermore, in most of the studies so far, hypertensive women have been examined collectively without addressing separately the issue of fetal growth and its interaction on maternal cardiovascular physiology.
The objective of this study was to prospectively investigate maternal cardiac function and peripheral haemodynamics in the first trimester of pregnancy to study the cohort according to eventual pregnancy outcome and assess its impact on screening for pre-eclampsia and SGA.