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Diabetes Mellitus incidence and its negative outcomes have dramatically increased worldwide and are expected to further increase in the future due to a combination of environmental and social factors. Several methods of measuring glucose concentration in various body compartments have been described in the literature over the years. Continuous advances in technology open the road to novel measuring methods and innovative measurement sites. The aim of this comprehensive review is to report all the methods and products for non-invasive glucose measurement described in the literature over the past five years that have been tested on both human subjects/samples and tissue models. A literature review was performed in the MDPI database, with 243 articles reviewed and 124 included in a narrative summary. Different comparisons of techniques focused on the mechanism of action, measurement site, and machine learning application, outlining the main advantages and disadvantages described/expected so far. This review represents a comprehensive guide for clinicians and industrial designers to sum the most recent results in non-invasive glucose sensing techniques' research and production to aid the progress in this promising field.

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INTRODUCTION: Maternal corticosteroid administration for anticipated preterm birth is common; however, the corticosteroid effect on fetal ultrasound and cardiotocograph (CTG) remains contested. This study aimed to evaluate short-term ultrasound and CTG impact of (a) dexamethasone versus betamethasone (b) pooled corticosteroid effect. METHODS: Substudy of blinded randomized trial of dexamethasone versus betamethasone (given <34 weeks). Umbilical artery (UA), middle cerebral artery (MCA), ductus venosus (DV), and uterine artery Doppler, myocardial performance index (MPI), biophysical profile (BPP), and CTG measured pre-corticosteroid then 1, 2, 4, and 7 days post-corticosteroid. RESULTS: Of 47 fetuses (39 singleton; 4 dichorionic, diamniotic twins; and 4 monochorionic, diamniotic twins) in the February 2012-2013 period, 24 received dexamethasone and 23 betamethasone at average gestation 29.8 ± 2.9 weeks. Thirteen pregnancies (30%) had pre-corticosteroid fetal concerns (estimated weight <10th centile and/or abnormal UA/MCA Doppler). Few significant differences were seen post-corticosteroid: DV pulsatility index and right MPI initially decreased 15-20%, and average BPP decreased slightly on days 1-2. There were no major differential effects of dexamethasone versus betamethasone. DISCUSSION/CONCLUSION: No substantive post-corticosteroid effects were seen for most ultrasound/CTG measures in fetuses with heightened preterm birth risk but predominantly normal pre-corticosteroid measures. Clinically, this suggests avoiding overreliance on individual measures for delivery decisions post-corticosteroid; equally, multiple/marked ultrasound changes suggest true pathology and not corticosteroid effect.

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Kidney development is key to the long-term health of the fetus. Renal volume and vascularity assessed by 3D ultrasound (3D-US) are known markers of wellbeing, however, a lack of real-time image segmentation solutions preclude these measures being used in a busy clinical environment. In this work, we aimed to automate kidney segmentation using fully convolutional neural networks (fCNNs). We used multi-parametric input fusion incorporating 3D B-Mode and power Doppler (PD) volumes, aiming to improve segmentation accuracy. Three different fusion strategies and their performance were assessed versus a single input (B-Mode) network. Early input-level fusion provided the best segmentation accuracy with an average Dice similarity coefficient (DSC) of 0.81 and Hausdorff distance (HD) of 8.96 mm, an improvement of 0.06 DSC and reduction of 1.43 mm HD compared to our baseline network. Compared to manual segmentation for all models, repeatability was assessed by intra-class correlation coefficients (ICC) indicating good to excellent reproducibility (ICC 0.93). The framework was extended to support multiple graphics processing units (GPUs) to better handle volumetric data, dense fCNN models, batch normalization and complex fusion networks. This work and available source code provides a framework to increase the parameter space of encoder-decoder style fCNNs across multiple GPUs and shows that application of multi-parametric 3D-US in fCNN training improves segmentation accuracy.

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PURPOSE: In this study, we aimed to comprehensively evaluate risk factors, ultrasound estimation of fetal weight, prenatal management, and pregnancy outcomes of gastroschisis and omphalocele at a metropolitan Australian hospital. MATERIAL AND METHODS: This was a retrospective single-center cohort study from 2006 to 2014 at a tertiary hospital with colocated neonatal surgical facilities. Demographic, pregnancy, ultrasound, birth and neonatal data were compared between gastroschisis and omphalocele. Correlation between routine (Hadlock 1 &2) and specific (Siemer) estimated fetal weight (EFW) estimation formulae with birth weight (BW) was made for those 50 gastroschisis cases with ≥2 third trimester scans and last scan ≤2 weeks prior to birth. RESULTS: There were 126 abdominal wall defects: 83 gastroschisis and 43 omphalocele. Consistent with international literature, the average maternal age was lower for gastroschisis and rates of smoking higher, while there were more intrauterine deaths and pregnancy terminations in omphalocele. Gastroschisis mothers were more likely living outside Sydney, had more infections in pregnancy and were followed with a larger number of antenatal visits, with a shorter period from the last visit to birth. In omphalocele pregnancies, amniocentesis was more likely performed, with more abnormal results than in gastroschisis fetuses. All EFW formulae had a good correlation between Z score for the last US and actual BW (ICC 0.693-0.815), with Hadlock 2 being the best. Siemer formula had the best correlation from first to the last scan. Gastroschisis newborns were born earlier (36.8 versus 38.2 wks p = .001), with smaller birthweight (2.52 versus 3.03 kg, p < .001), a longer request of intensive care (central line, parenteral nutrition, intubation) and second surgery, along with more multisystem complications (average 1.5 versus 0.7, p = .004) and a longer hospital stay (58.8 versus 36.8 d, p < .001). CONCLUSION: Demographic, antenatal, and pregnancy outcome data for abdominal wall defects correlated well with the international literature. Hadlock 1-2 gave the most consistent EFW estimate, with all formulae showing good correlation.

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BACKGROUND: Bimanual clot evacuation (BCE) is a simple clinical manoeuvre that may reduce need for surgical intervention in the management of severe postpartum haemorrhage (PPH). We sought to determine whether performing BCE in cases of severe PPH after vaginal birth reduces the need for surgical intervention. METHODS: A retrospective chart review of women who delivered vaginally with a severe PPH between January 1, 2011 and December 31, 2014 in a single tertiary women's hospital in Sydney, Australia was conducted. Severe PPH was classified as a blood loss ≥1000mls. The need for surgical management (including operating theatre uterine exploration or evacuation, intrauterine balloon tamponade, repair of significant trauma, uterine or internal iliac artery ligation, B-Lynch suture insertion or hysterectomy) was the primary outcome measure, as expressed by need for operating theatre utilisation. RESULTS: From a cohort of 438, 149 women (34.0%) had BCE, of whom 29 (19.5%) required surgical management compared to 103 of 289 women with no BCE (35.6%); an odds ratio (OR) of 0.38 for BCE (confidence interval 0.20-0.72; p = 0.003). Early BCE (< 1 h of delivery) was associated with a further reduction in surgery (OR 0.24; confidence interval 0.08-0.70; p = 0.009) compared to late BCE (> 1 h of delivery). There was no reduction in estimated blood loss (p = 0.86) or blood transfusion (p = 0.71) with BCE. CONCLUSION: Our study suggests BCE reduces theatre utilisation in the context of severe PPH following vaginal delivery. Prospective trials are needed to determine whether BCE should be endorsed as a treatment modality for PPH post-vaginal delivery.

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BACKGROUND: Placental perfusion can be evaluated by 3D power Doppler ultrasound (3D PD-US), particularly using the validated tool 3D Fractional Moving Blood Volume (3D-FMBV); however regional variability and size limitations beyond the first trimester mean that multiple 3D PD-US volumes are required to evaluate the whole organ. PURPOSE: We assessed the feasibility of manual offline stitching of second trimester 3D PD-US volumes of the placenta to assess whole organ perfusion using 3D-FMBV. MATERIALS AND METHODS: This was a single-centre, prospective, observational cohort study of 36 normal second trimester singleton pregnancies with anterior placentas. 3D PD-US placental volumes were manually segmented offline and stitched together by rigid registration using manually selected, pair-wise coordinates. Data acquisition and offline volume segmentation and stitching were triplicated by a single observer with Dice similarity coefficient (DSC) and Hausdorff distance used to assess consistency. Intraclass correlation coefficient (ICC) was used to assess intra-observer repeatability of 3D-FMBV and placental volume. RESULTS: Acquisition and stitching success were 94% and 88%, respectively. Median time for acquisition, segmentation and stitching were 13 min, 40 min and 95 min, respectively. Median intra-observer DSCs were 0.94 and 0.88, and Hausdorff distances were 11.85 mm and 36.6 mm, for segmentations and stitching, respectively. CONCLUSION: 3D-ultrasound volume stitching of the placenta is technically feasible. Intra-observer repeatability was good to excellent for all measured parameters. This work demonstrates technical feasibility; further studies may provide the basis of an in-vivo assessment tool to measure the placenta in mid-to late pregnancy.

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Background Three-dimensional (3D) fractional moving blood volume (FMBV) derived from 3D power Doppler US has been proposed for noninvasive approximation of perfusion. However, 3D FMBV has never been applied in animals against a ground truth. Purpose To determine the correlation between 3D FMBV and the reference standard of fluorescent microspheres (FMS) for measurement of renal perfusion in a porcine model. Materials and Methods From February 2017 to September 2017, adult pigs were administered FMS before and after measurement of renal 3D FMBV at baseline (100%) and approximately 75%, 50%, and 25% flow levels by using US machines from two different vendors. The 3D power Doppler US volumes were converted and segmented, and correlations between FMS and 3D FMBV were made with simple linear regression (r2). Similarity and reproducibility of manual segmentation were determined with the Dice similarity coefficient and 3D FMBV reproducibility (intraclass correlation coefficient [ICC]). Results Thirteen pigs were studied with 33 flow measurements. Kidney volume (mean Dice similarity coefficient ± standard deviation, 0.89 ± 0.01) and renal segmentation (coefficient of variation = 12.6%; ICC = 0.86) were consistent. The 3D FMBV calculations had high reproducibility (ICC = 0.97; 95% confidence interval: 0.96, 0.98). The 3D FMBV per-pig correlation showed excellent correlation for US machines from both vendors (mean r2 = 0.96 [range, 0.92-1.0] and 0.93 [range, 0.78-1.0], respectively). The correlation between 3D FMBV and perfusion measured with microspheres was high for both US machines (r2 = 0.80 [P < .001] and 0.70 [P < .001], respectively). Conclusion The strong correlation between three-dimensional (3D) fractional moving blood volume (FMBV) and fluorescent microspheres indicates that 3D FMBV shows excellent correlation to perfusion and good reproducibility. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Morrell et al in this issue.

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BACKGROUND: The measurement and interpretation of patient experience is a distinct dimension of health care quality. The Midwives @ New Group practice Options (M@NGO) randomized control trial of caseload midwifery compared with standard care among women regardless of risk reported both clinical and cost benefits. This study reports participants' perceptions of the quality of antenatal care within caseload midwifery, compared with standard care for women of any risk within that trial. METHODS: A trial conducted at two Australian tertiary hospitals randomly assigned participants (1:1) to caseload midwifery or standard care regardless of risk. Women were sent an 89-question survey at 6 weeks postpartum that included 12 questions relating to pregnancy care. Ten survey questions (including 7-point Likert scales) were analyzed by intention to treat and illustrated by participant quotes from two free-text open-response items. RESULTS: From the 1748 women recruited to the trial, 58% (n = 1017) completed the 6-week survey. Of those allocated to caseload midwifery, 66% (n = 573) responded, compared with 51% (n = 444) of those allocated to standard care. The survey found women allocated to caseload midwifery perceived a higher level of quality care across every antenatal measure. Notably, those women with identified risk factors reported higher levels of emotional support (aOR 2.52 [95% CI 1.87-3.39]), quality care (2.94 [2.28-3.79]), and feeling actively involved in decision-making (3.21 [2.35-4.37]). CONCLUSIONS: Results from the study show that in addition to the benefits to clinical care and cost demonstrated in the M@NGO trial, caseload midwifery outperforms standard care in perceived quality of pregnancy care regardless of risk.

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Medical informed consent is the process by which a 'competent', non-coerced individual receives sufficient information including risks of a medical procedure and gives permission for it to occur. The capacity to give an informed consent might be impaired during labour. This study aimed to examine women's abilities to understand and remember during labour. Women were prospectively recruited at 36 weeks of gestation and randomised to undertake questionnaires which assessed their ability to understand and remember information. They were randomised to: (1) information given in labour only, written format (2) information in labour, verbal (3) information at 36 weeks plus labour, written (4) information at 36 weeks plus labour, verbal. Immediate comprehension and retention was assessed at 36 weeks, in labour, and 24-72 hours after birth. Forty-nine women completed the questionnaires regarding understanding and retention of information at 36 weeks, six intrapartum, and five postpartum (90% attrition). Women receiving information at 36 weeks and in labour versus in labour had a higher comprehension of pregnancy-related information, its retention, and total score. Women receiving information in late pregnancy and labour may comprehend and retain it better than women only receiving information during labour. Given small sample size, further research is needed to support these preliminary findings. Impact statement What is already known on this subject? The evidence regarding the capacity of labouring women to give informed consent is largely based on women's self-reported experiences or expert opinions and has mixed findings. Existing guidelines recommend that an informed consent should be given antenatally for both clinical practice and research. Studies show that obtaining an informed consent antenatally is neither feasible nor widely implemented. What do the results of this study add? A novel approach to providing empirical evidence regarding women's capacity to comprehend and retain information during labour. Our study confirms the difficulty with antenatal recruitment for intrapartum research. What are the implications of these findings for clinical practice and/further research? This raises ethical concerns regarding the current intrapartum research in which consent is largely sought at the time of the study. Emphasises the need to explore the question 'Do labouring women have the capacity to consent to research?' in order to ensure that women are protected during labour.

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INTRODUCTION: To assess fetal vs. neonatal diagnoses, pregnancy outcomes and need for surgery in babies prenatally diagnosed with congenital pulmonary airway malformation (CPAM) or bronchopulmonary sequestration (BPS). METHODS: Retrospective single-centre cohort study of fetuses with a prenatal diagnosis of CPAM or BPS between 2006 and 2014. Data collected included serial antenatal ultrasound information and neonatal/infant diagnoses and outcomes. RESULTS: Initial ultrasound diagnosis (n = 63) was CPAM in 51 and BPS in 12: nineteen (30%) fetuses had mediastinal shift and 2 (3%) had hydrops. All neonates with known birth outcome (n = 56) were liveborn. Final diagnosis in 52 infants (83%) with neonatal imaging and/or histopathology confirmed CPAM in 17/44 (39%) and BPS in 6/9 (67%). Of 34 prenatally suspected but unconfirmed CPAM lesions: 10 had no lesion on neonatal imaging, one no neonatal imaging performed, five confirmed BPS, 11 other lung/thoracic lesions, seven were lost to follow-up. There was one infant death. 27/63 infants (43%) had post-natal surgery. More neonates requiring neonatal respiratory support/resuscitation had surgery compared to those who did not (67% vs. 29%, P = 0.008). Patients with suspected CPAM or BPS on both initial and final ultrasound were more likely to have post-natal surgical management than when a lesion was no longer visible on final antenatal ultrasound (68% vs. 23%, P = 0.001). CONCLUSIONS: Over 50% of antenatally suspected CPAM/BPS either regressed or had an alternate post-natal diagnosis. Perinatal outcome was good, with the majority of neonates/infants conservatively managed. Persistently visible antenatal lesion and need for neonatal respiratory support predicted ultimate surgical management.

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AIMS: Assess clinical utility of the foetal Myocardial Performance Index (MPI) in evaluation and management of monochorionic, diamniotic twin (MCDA) pregnancies. METHODS: Prospective cohort of (a) initially uncomplicated MCDA (b) Complicated MCDA, including twin-twin transfusion syndrome (TTTS), selective intrauterine growth restriction (sIUGR), and liquor and/or growth discordance (L/GD) not meeting TTTS or sIUGR criteria. TTTS and sIUGR were case-control matched. Routine Dopplers and MPI were taken and correlated to diagnosis and final outcome. RESULTS: Twenty-six always uncomplicated pairs, 51 always complicated pairs, and seven uncomplicated to pathological pairs were included. TTTS recipient (n = 25) left and right MPI and intertwin difference (ITD) were significantly elevated, however, were already elevated in Stage I (n = 10), and did not predict progression or pregnancy outcome. sIUGR MPI (n = 11) did not differ significantly from control. Of 15-L/GD pairs, two that progressed to TTTS had significantly higher left and right MPI values in the future recipient (0.61 and 0.72) versus future sIUGR larger twins (0.48 and 0.51) or stable L/GD (0.47 and 0.52): p < .01 for all comparisons. CONCLUSIONS: In this cohort, MPI did not add substantial diagnostic/prognostic information to current routine evaluation in established TTTS or sIUGR though potentially differentiated L/GD cases progressing to TTTS.

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The goal of our research was to quantify the placental vascularity in 3-D at 11-13 + 6 wk of pregnancy at precise distances from the utero-placental interface (UPI) using 3-D power Doppler ultrasound. With this automated image analysis technique, differences in vascularity between normal and pathologic pregnancies may be observed. The algorithm was validated using a computer-generated image phantom and applied retrospectively in 143 patients. The following features from the PD data were recorded: The number of spiral artery jets into the inter-villous space, total geometric and PD area. These were automatically measured at discrete millimeter distances from the UPI. Differences in features were compared with pregnancy outcomes: Pre-eclamptic versus normal, all small-for-gestational age (SGA) to appropriate-for-gestational age (AGA) patients and AGA versus SGA in normotensives (Mann-Whitney). The Benjamini-Hochberg procedure was used (false discovery rate 10%) for multiple comparison testing. Features decreased with increasing distance from the UPI (Kruskal-Wallis test; p <0.001). At 2- 3 mm from the UPI, all features were smaller in pre-eclamptic compared with normal patients and for some in SGA compared with AGA patients (p <0.05). For AGA versus SGA in normotensive patients, no significant differences were found. Number of jets measured at 2-5 mm from the UPI did not vary because of the position of the placenta in the uterus (ANOVA; p > 0.05). This method provides a new in-vivo imaging tool for examining spiral artery development through pregnancy. Size and number of entrances of blood flow into the UPI could potentially be used to identify high-risk pregnancies and may provide a new imaging biomarker for placental insufficiency.

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OBJECTIVES: To determine whether there are any fetal cardiac function changes, as measured by the myocardial performance index (MPI), in pregnancies complicated by decreased fetal movement (DFM). METHODS: We performed a prospective cross-sectional case-control study of 50 DFM and 50 uncomplicated third-trimester pregnancies matched within 2 gestational weeks. Routine ultrasound growth and well-being parameters as well as MPI were measured. Average MPI measurements and its component values were compared between the DFM and the control group, as were demographics, other ultrasound data, and perinatal outcomes. RESULTS: Average left MPI (LMPI) and right MPI (RMPI) was similar between groups (LMPI: 0.54 ± 0.08 [DFM], 0.53 ± 0.08 [controls], p = 0.76; RMPI: 0.60 ± 0.12 (DFM), 0.59 ± 0.11 [controls], p = 0.79). However, subgroup analysis of DFM fetuses with (n = 20) or without (n = 30) any adverse perinatal outcome demonstrated modestly higher average RMPI and LMPI in the adverse perinatal outcome group (RMPI: 0.64 ± 0.08 vs. 0.57 ± 0.13, p = 0.02; LMPI: 0.56 ± 0.07 vs. 0.52 ± 0.07, p = 0.052). CONCLUSION: The MPI did not demonstrate clinically usable differences between the overall DFM population and controls. However, higher LMPI and RMPI values in the exploratory subgroup of DFM fetuses with adverse perinatal outcomes may warrant further exploration of the MPI in DFM.

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INTRODUCTION: Spatiotemporal image correlation (STIC) can evaluate fetal renal impedance using four-dimensional volumetric indices. We assessed repeatability of three-dimensional kidney segmentation and the repeatability of the resultant indices. METHODS: In each of 57 healthy pregnant women, three renal artery pulsed-wave Doppler (PWD) traces and three STIC volumes were acquired from the same fetal kidney and segmented by two observers. Vascularisation-flow index (VFI) and fractional moving blood volume (FMBV) were calculated for every STIC frame and used to determine the volumetric pulsatility index (vPI), volumetric resistance index (vRI) and volumetric systolic/diastolic ratio (vS/D). Segmentation performance was assessed using Dice similarity coefficients (DSCs), Hausdorff distances, coefficient of variation (CoV) and the intraclass correlation coefficient (ICC). Intra/Inter volumetric index repeatability was assessed using ICCs. RESULTS: Forty-eight cases (84%) provided full data. Mean intra- and interobserver DSCs were 0.90 and 0.81. Mean intra- and interobserver Hausdorff distances were 3.88 mm and 5.27 mm. Average kidney volumes for observers 1 and 2 were 9.88 mL and 8.54 mL (mean difference 16.1%). Mean intra-observer volumetric CoVs were 5.3% and 8.1%. Intra- and interobserver ICCs for kidney volume (same STIC volume) were 0.97 and 0.85. When assessing volume variation between STIC volumes, intra-observer ICC was 0.97. ICCs were 0.77-0.81 for VFI-derived volumetric indices and 0.61-0.62 for FMBV-derived indices; ICCs for all PWD indices were between 0.58 and 0.59. CONCLUSIONS: Periodical variation in vascularity was demonstrated in the fetal kidney, and three-dimensional segmentation was highly repeatable. Derived volumetric impedance indices show moderate variability but outperform corresponding two-dimensional PWD indices in terms of reproducibility.

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OBJECTIVES: To compare the repeatability and degree of absolute agreement of an automated fetal right myocardial performance index (MPI) algorithm with manual measurements along with the impact of MPI observer experience on these two aspects. METHODS: Prospective cross-sectional study of 65 uncomplicated singleton pregnancies from 22 to 39 weeks' gestation. Image analysis of double-waveform right MPI measurements was conducted first with a MATLAB automated MPI software and then independently by an experienced and an inexperienced observer. Intraclass correlation coefficients (ICCs) and 95% confidence intervals (95% CI) were used to evaluate manual and automated intra- and interobserver repeatability. In addition, Bland-Altman plots were used to determine the degree of absolute agreement. RESULTS: Successful automation was performed on 63 cases (97%) showing repeatability ICCs of: 0.83 manual intraobserver; 0.77 manual interobserver; 1.00 automated. The degree of absolute agreement between manual and automated values was: inexperienced observer ICC 0.43 (95% CI 0.21-0.62); experienced observer ICC 0.76 (95% CI 0.63-0.85). CONCLUSION: Automation of right MPI demonstrates a superior reproducibility over manual measurements and reduces the experience required for successful analysis. This may lend a greater clinical applicability to MPI, and future studies to develop an automated universal reference range would be useful.

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OBJECTIVE: To undertake an observational study to see whether first trimester placental vascularity, measured with a standardized power Doppler index: 3D-FMBV, is different in pregnancies which either develop pre-eclampsia or lead to term, normotensive small for gestational age (SGA) babies. METHODS: Women were scanned between 11 and 13+6 weeks. The placental volume (sPlaV) was estimated using our previously validated semi-automated tool. Estimates of 3D-FMBV were generated from the raw power Doppler signal for the whole utero-placental interface, UPI (FMBV-UPI) and 5mm into the placenta (FMBV-IVS). Differences in the placental volume and FMBV for pregnancies developing pre-eclampsia and resulting in term, normotensive SGA babies were compared with term, normotensive, appropriate for gestational age (AGA), controls. RESULTS: Results were available for 143 women. The placental volume (sPlaV) was reduced in both pre-eclampsia (p = 0.007) and term, normotensive SGA (p = 0.001) when compared with term normotensive AGA controls. 3D-FMBV estimates were significantly lower for pregnancies developing pre-eclampsia (FMBV-UPI, p = 0.03, FMBV-IVS, p = 0.01) but not for the normotensive SGA pregnancies (FMBV-UPI, p = 0.16, FMBV-IVS, p = 0.27). CONCLUSION: Pregnancies destined to develop pre-eclampsia are more likely to have small placentas with significantly reduced vascularity at 11-13 weeks. Those pregnancies which were normotensive throughout but resulted in an SGA baby delivered at term, had significantly smaller placentas but with similar vascularity to normotensive AGA pregnancies.

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OBJECTIVE: We aimed to assess the feasibility of assessing the fetal right Myocardial Performance Index (RMPI) using single waveform and to compare absolute values with dual technique. METHODS: We studied 145 morphologically normal appropriately grown fetuses at 16-28 weeks' gestation with local Ethics Committee approval using fixed machine settings: Doppler sweep velocity at 15 cm/s; angle of insonation <150; wall motion filter 300 Hz. Doppler gate was 3 mm, increased to 4-5 mm if needed. RMPI was obtained twice in the same fetus; using 'dual-image' and 'single-image' techniques. Dual images were acquired as previously described. Single images were taken from the tip or just below the tricuspid valve towards the ventricular septum in the apical four-chamber view. RMPI was calculated using two-value (a-b/b) or three-value (ICT+IRT/ET) formulae where 'a', 'b' or (ET) represent the isovolumetric and ejection times, and ICT and IRT represent the isovolumetric contraction and relaxation times. RESULTS: Dual image was accessible in 100% of fetuses. Single-image acquisition was 100%, 92.3% and 76.5% at 16+0-24+0, 24+1-27+0, and 27+1-28+0 weeks respectively (95.2% overall). Doppler gate increased in 23 cases (16.6%); 8/17 (47%) at 27+1-28+0 weeks' gestation. Mean and standard deviation for 'dual image' and 'single image' were: RMPI 0.46 ± 0.09 and 0.49 ± 0.07; 'a' 249.06 ± 11.50 and 249.11 ± 11.93; 'b' 170.85 ± 8.95 and 167.62 ± 8.39. CONCLUSIONS: Single-image acquisition RMPI is highly feasible from 16 to 26 weeks gestation. Difference in mean values may represent overestimation of ejection time in the 'dual-image' technique.

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OBJECTIVES: 4D (3D + time) indices of tissue impedance using power Doppler (PD) ultrasound (US) can be measured with spatial-temporal image correlation (STIC) imaging. We wished to evaluate their repeatability and their influence under changes to US machine settings and regional differences within the placenta. METHODS: A total of 46 healthy women were recruited at 20-34 weeks of gestation. A total of 9940 3D frames from 644 4D data sets were analysed providing both 3D and 4D indices of vascularity. 4D vs. 3D indices were compared with different machine settings, across the cardiac cycle and in the different placenta regions to assess regional variability. RESULTS: 3D and 4D indices significantly decreased as wall motion filter (WMF) was increased (P < 0.001). Repeatability decreased as WMF increased (ICC; low1 = 0.80; high1 = 0.60). Indices were significantly lower at the maternal aspect (P = 0.002-0.009) of the placenta and showed less repeatability (ICC; 0.42-0.79) than the fetal aspect (ICC 0.49-0.88). 4D repeatability was good in the central region (ICC 0.80-0.81) but poor in the periphery (ICC 0.45-0.59), while 3D indices were good and comparable between regions (ICC; 0.80 central; 0.81 peripheral). CONCLUSIONS: This study supports the future use of WMF 'low1' and PD to generate more reliable 4D indices values. For 3D indices, HD Flow may improve Doppler signal sensitivity. Regarding placental regional variability, the fetal plate and the central region demonstrated more repeatable 4D indices. 4D PD indices have potential to overcome the limitations of VOCAL™ indices and provide an internally standardised measure of localised impedance in vascular beds.

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The aortic isthmus (AoI) is a unique fetal watershed with a waveform reflecting its complex haemodynamic physiology. The systolic component represents left and right ventricular systolic ejection, and the diastolic component represents comparative downstream vascular impedance between the brachiocephalic and subdiaphragmatic fetal circulations. Several indices have been devised to quantify different components of the waveform, including the pulsatility index, resistance index, isthmic flow index, and recently the isthmic systolic index. There have been promising preliminary studies applying these indices to both cardiac (congenital) and extracardiac pathologies, including intrauterine growth restriction and twin-twin transfusion syndrome. However, the waveform's multifactorial origin has proven to be challenging, and the difficulty in separating various components of the waveform could explain that AoI evaluation does not have a clear clinical utility. Further research is underway to realise the full potential of this vessel in fetal cardiac and haemodynamically compromised pathological conditions. In this review article we outline the physiological origin of this Doppler waveform, describe in detail the various published indices, summarise the published literature to date, and finally outline potential future research and hopefully clinical applications.

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