Impedance cardiography in uncomplicated pregnancy and pre-eclampsia: a reliability study

It has been reported that cardiac contractility is altered in pre-eclampsia compared with normal pregnancy. Because of the non-invasive nature of impedance cardiography (ICG), this method is gaining popularity in the obstetric field. We assessed the reliability of ICG measurements in uncomplicated 3rd trimester pregnancies (UP) and pre-eclamptic pregnancies (PE). ICG measurements were recorded before and after three position changes, and this examination was done twice (session 1 and 2) per subject. For each of the 22 haemodynamic parameters, inter- and intrasession Pearson's correlation coefficients (PCC) were calculated for mean values of 30 measurements per position per subject. PCC was consistently ≥ 0.80 for contractility parameters 'acceleration-', 'velocity-' and 'heather-index' in both UP and PE. These data illustrate that correlation between repeated ICG measurements of cardiac contractility is high under standardised conditions, and that ICG may be useful to study changes of cardiac contractility in pregnancy.