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Background: Due to the importance of cardiovascular dysfunction and advances in the development and use of non-invasive cardiac output (CO) monitoring devices, there is a growing interest in their use in the obstetric population. The aim of this study was to compare two commercially available, non-invasive CO monitors in the assessment of heart rate (HR), stroke volume (SV), CO, cardiac index (CI) and total peripheral resistance (TPR) in an obstetric population. Methods: This was a prospective, comparative study including two groups. A normotensive group, which consisted of uncomplicated healthy pregnancies, and a hypertensive group, which consisted of those complicated by hypertensive disorders of pregnancy. Non-invasive cardiovascular assessments were performed using two methodologies. USCOM® is an operator-dependent Doppler ultrasound device which obtains velocity time integrals of transaortic blood flow at the left ventricular outflow tract, while NICOM® provides an operator-independent haemodynamic profile by assessing thoracic voltage changes (bioreactance) which reflect pulsatile blood flow in the thorax. Correlation coefficients were derived, and Bland-Altman analysis was performed to derive the mean percentage difference (MPD) between the devices. Results: 598 women were recruited for this study. In the normotensive group, 524 paired results were analysed, while 74 paired results were analysed in the hypertensive group. In the normotensive group, we found excellent correlation between USCOM® and NICOM® for HR (r = 0.885, p < 0.05), and moderate correlations for SV (r = 0.445, p < 0.05), CO (r = 0.529, p < 0.05), CI (r = 0.385, p < 0.05) and TPR (r = 0.524, p < 0.05). In the hypertensive group, we obtained similar correlations (HR: r = 0.877, p < 0.05; SV: r = 0.575, p < 0.05; CO: r = 0.601, p < 0.05; TPR: r = 0.589, p < 0.05). Bland-Altman analysis found that the agreement between both methodologies improved as gestation advances, with an MPD of 34% for CO estimation in the third trimester of uncomplicated pregnancies, and 39% in pregnancies complicated by hypertensive disorders. Conclusion: Our findings suggest that the two methodologies perform similarly in both uncomplicated pregnancies and in pregnancies complicated by hypertensive disorders. The study findings do not preclude the use of USCOM® and NICOM® devices in pregnancy, but indicate that these platforms cannot be used interchangeably. Our findings demonstrate an improvement in MPD as gestation advances and, therefore, questions the validity of previous longitudinal studies investigating maternal haemodynamics using these methodologies. Our work also highlights the need to construct reference ranges for each device and for validation of each methodology against a reference method before their use in research or clinical practice.

Objective: To evaluate the umbilical cord venous S100β levels in late-pregnancy fetuses with abnormal growth and cerebral redistribution. Methods: The pulsatility index of the umbilical and middle cerebral arteries and the cerebroplacental ratio (CPR) were measured in 132 fetuses at ≥34 weeks, and the CPR was converted into multiples of the median (MoM). A blood sample from the umbilical vein was collected at birth, and the umbilical venous S100β levels were evaluated in small and non-small for gestational age (SGA) fetuses, with and without abnormal Doppler indices. The levels of S100β were correlated with birth weight (BW) centile, CPR MoM and cord venous pH. Results: While CPR MoM correlated with BW centile, S100β showed no correlation with any of the studied fetal parameters. In addition, no differences were observed in S100β level according to BW centile or Doppler parameters, neither was there any difference between SGA with low CPR MoM and non-SGA with normal CPR MoM. Conclusion: Late-pregnancy fetuses with abnormal growth or cerebral redistribution have normal cord blood levels of S100β at birth. In these fetuses, the potential consequences of chronic hypoxemia on the fetal brain might not be detectable using tissue necrosis markers.

The aim of this study was to compare time-domain waveform analysis of second-trimester uterine artery Doppler using the resistance index (RI) with waveform analysis using a mathematical tool known as wavelet transform for the prediction of pre-eclampsia (PE). This was a retrospective, nested case-cohort study of 336 women, 37 of whom subsequently developed PE. Uterine artery Doppler waveforms were analysed using both RI and waveform analysis. The utility of these indices in screening for PE was then evaluated using receiver operating characteristic curves. There were significant differences in uterine artery RI between the PE women and those with normal pregnancy outcome. After wavelet analysis, significant difference in the mean amplitude in wavelet frequency band 4 was noted between the 2 groups. The sensitivity for both Doppler RI and frequency band 4 for the detection of PE at a 10% false-positive rate was 45%. This small study demonstrates the application of wavelet transform analysis of uterine artery Doppler waveforms in screening for PE. Further prospective studies are needed in order to clearly define if this analytical approach to waveform analysis may have the potential to improve the detection of PE by uterine artery Doppler screening.