Three-Dimensional Fractional Moving Blood Volume: A Robust Bedside Tool for Evaluation of Fetal Multiorgan Perfusion.

INTRODUCTION: Three-dimensional fractional moving blood volume (3D-FMBV) may provide superior noninvasive measurement of feto-placental perfusion compared to current methods. This study investigated the feasibility and repeatability of producing 3D-FMBV measurements of the placenta, fetal liver, kidney, and brain in a single ultrasound consultation. METHODS: The placenta, fetal liver, kidney, and brain were scanned in triplicate using 3D power Doppler ultrasound (3D-PDU) in 48 women ≥22 weeks of gestation with healthy fetuses. 3D-FMBV was calculated by two analyzers. Feasibility was assessed as the percentage of cases where 3D-FMBV could be evaluated; repeatability (intraobserver and interobserver) using two-way mixed measure intraclass correlation coefficients (ICCs). RESULTS: 3D-FMBV was calculated for 100% of scanned organs. Intraobserver ICCs (95% CI) were good to excellent; 0.93 (0.88-0.96) and 0.87 (0.78-0.92) for placenta, 0.95 (0.92-0.97) and 0.98 (0.96-0.99) for fetal liver, 0.96 (0.94-0.98) and 0.91 (0.85-0.95) for fetal kidney, and 0.98 (0.97-0.99) and 0.97 (0.95-0.98) for fetal brain. Interobserver ICCs (95% CI) were 0.50 (0.08-0.73), 0.92 (0.85-0.96), 0.89 (0.78-0.94), and 0.71 (0.46-0.85) for placenta, fetal liver, kidney, and brain. CONCLUSION: Feto-placental perfusion assessment with 3D-FMBV is highly reliable in healthy pregnancies ≥22 weeks of gestation and can be feasibly calculated in four feto-placental vascular beds in a single ultrasound consultation.

The Influence of Hyperoxygenation on Fetal Brain Vascularity Measured Using 3D Power Doppler Ultrasound and the Index "Fractional Moving Blood Volume".

INTRODUCTION: Maternal hyperoxygenation effects on fetal cerebral hemodynamics are largely unknown. This study aimed to determine efficacy and reliability of a validated power Doppler ultrasound (US) index, fractional moving blood volume (FMBV), at measuring fetal cerebral vasculature changes during maternal hyperoxia. METHODS: The fetal cerebral effects of 10 min of hyperoxygenation at 2 flow rates (52%/60% FiO2) were evaluated in women in their third trimester of pregnancy. 2D-US and 3D-US in a transverse plane were performed before, during, and following maternal hyperoxygenation with FMBV estimation performed offline. RESULTS: Forty-five cases provided data for analysis. Mean intraobserver ICCs were 0.89 (3D-FMBV) and 0.84 (2D-FMBV). A significant difference in vascularity before and during and before and after 60% hyperoxia was observed (p < 0.05), whereas no significant differences were found at 52% hyperoxia (p > 0.05). Significant differences in vascularity were found between 2D-FMBV and 3D-FMBV (p < 0.01). CONCLUSION: Measurement of fetal cerebral vascularity by 3D-FMBV and 2D-FMBV was highly reproducible. The differing cerebral vascular changes seen with 60% but not 52% FiO2 suggest a possible "threshold effect" that may have influenced prior studies. Further studies are needed to assess cerebral effects of maternal hyperoxygenation on compromised fetuses.

Audit of immediate outcomes for MCDA twins following laser therapy for twin-twin transfusion syndrome at the NSW Fetal Therapy Centre.

OBJECTIVE: To audit immediate pregnancy and neonatal outcomes of selective laser photocoagulation of communicating vessels (SLPCV) for twin-twin transfusion syndrome (TTTS) at the New South Wales Fetal Therapy Centre. METHODS: Retrospective cohort study of 151 TTTS cases undergoing SLPCV between July 2003 and May 2013, evaluating procedural details, delivery and perinatal outcomes. RESULTS: The majority of cases were Stage III at SLPCV (56.9%), although proportion of Stage II SLPCV increased over time (P = 0.03). Survival to hospital discharge of at least one baby was 85.6% and dual survival was 52.5%. Median gestational age at delivery was 32.6 weeks (IQR 29.0-35.0 weeks) with a median of 11.4 weeks (IQR 8.3-14.7) from laser to delivery. Median birthweight was 1792 g (IQR 1288-2233 g), with 75% of babies admitted to the nursery, predominantly secondary to prematurity. Immediate SLPCV complications were in utero fetal demise <1 week postprocedure in 27 fetuses (19.6%) and/or ruptured membranes <1 week postprocedure in 9 fetuses (6.6%). CONCLUSIONS: This Australian series shows that local outcomes after SLPCV for stages II-IV TTTS remain equal to the international published literature and have remained stable after an initial learning curve. Women were more likely to be Stage II rather than III in the more recent years. However, this does not appear to be attributable to altered referral patterns.

Is Averaging of Three Waveforms Sufficient to Generate a Truly Representative Value for Pulsed-Wave Doppler Measures of Impedance?

OBJECTIVE: We aimed to evaluate the physiological variation in common pulsed-wave Doppler (PWD) indices of impedance to determine the number of waveforms to be averaged to minimise variability to 5%. METHODS: A single-centre, prospective, cross-sectional cohort study of uncomplicated singleton pregnancies at 20-37 week's gestation. From each patient 100 PWD waveforms were acquired including the umbilical artery (UA), middle cerebral artery (MCA) and uterine arteries (UtAs), with 30 waveforms acquired from the ductus venosus. Each waveform was individually measured using the machine's in-built software in automated mode. The variability was assessed using coefficient of variation. The number of waveforms to be averaged was calculated using the moving average and standard error of mean. RESULTS: From a cohort of 200 pregnancies, a total of 189 were analysed. The pulsatility index (PI) demonstrated greater variability compared with the resistance index (RI) in all vessels studied. A minimum of 14 UA and MCA, and 13 UtA PWD waveforms were required to reduce PI variability to 5%, while only 2 RI waveforms were required for UA, 1 for MCA and 8 for UtAs. CONCLUSION: The variability shown across all PWD indices and between vessels means that PWD indices results should be interpreted cautiously and averaged over multiple waveforms. Consideration should be given to adoption of RI, as it showed greater stability than PI for maternal-fetal Doppler.