The Aortic Isthmus: A Significant yet Underexplored Watershed of the Fetal Circulation

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.

Uncommon complications of monochorionic twin pregnancies: Twin anaemia-polycythaemia sequence

Introduction

Twin anaemia-polycythaemia sequence (TAPS) occurs when significant haemoglobin discordance exists between monochorionic fetuses. Most reported cases occur iatrogenically after twin-to-twin transfusion syndrome (TTTS) laser therapy; spontaneous TAPS is also reported. The purpose of this study was to investigate pregnancy management and immediate neonatal outcomes for monochorionic multiple pregnancies complicated by TAPS referred to the NSW Fetal Therapy Centre (FTC).

Methods

Retrospective cohort study of multiple pregnancies referred to NSW FTC between April 2006 and April 2014. Fourteen TAPS cases [discordant middle cerebral artery peak systolic volume (MCA-PSV) or clinician diagnosis antenatally, or Hb >20 g/dL vs. <12 g/dL post-natally] were compared to an existing TTTS database (n = 142) and uncomplicated monochorionic diamniotic (MCDA) twin pregnancies (n = 45). Outcomes measured were maternal demographics; ultrasound findings at referral; management, including whether in utero fetal therapy was performed; and pregnancy outcome, including gestation at birth, mode of birth, birthweight, fetal/neonatal complications and neonatal survival to discharge.

Results

The majority of TAPS cases were spontaneous (9/14) and occurred later in pregnancy than TTTS (median gestation at diagnosis 26.0 ± 4.9 vs. 20.4 ± 2.6 weeks, P < 0.001). However, TAPS perinatal outcome was similar to TTTS (survival of both twins 62% vs. 53%, survival of at least one twin 85% vs. 87%, overall survival 73% vs. 70%) and overall survival significantly lower than for uncomplicated MCDA pregnancies (73% vs. 98%, P < 0.001).

Conclusion

Overall mortality for TAPS was similar to that of TTTS but significantly higher compared to uncomplicated MCDA pregnancies, underscoring the potential severity of TAPS despite its later gestational onset.

Review of the correlation between blood flow velocity and polycythemia in the fetus, neonate and adult: appropriate diagnostic levels need to be determined for twin anemia-polycythemia sequence

Twin anemia-polycythemia sequence (TAPS) is recognized increasingly antenatally by the demonstration of an anemic twin and a polycythemic cotwin using the middle cerebral artery peak systolic velocity (MCA-PSV). While the MCA-PSV has been shown to correlate well with anemia in singleton fetuses, the evidence to support its use to diagnose fetal polycythemia appears to be less clear-cut. We aimed to evaluate fetal, neonatal and adult literature used to support the use of MCA-PSV for the diagnosis of polycythemia. Comprehensive literature searches were performed for ultrasound evidence of polycythemia in the human fetus, neonate and adult using key search terms. Only manuscripts in the English language with an abstract were considered for the review, performed in June 2014. Fifteen manuscripts were found for the human fetus, including 38 cases of TAPS. Nine of these defined fetal polycythemia as MCA-PSV < 0.8 multiples of the median (MoM), five used < 1.0 MoM and one used 0.8-1.0 MoM. Only two studies, involving a total of 15 cases, proposed a diagnostic level, acknowledging false-positive and -negative cases, though neither reported sensitivities or specificities. Six neonatal studies (96 neonates) demonstrated evidence of decreased cerebral velocities in polycythemia and a consequent increase with hemodilution. In the adult, five studies (57 polycythemic adults) demonstrated increased flow or velocity with hemodilution. Neither neonatal nor adult studies conclusively defined levels for screening for polycythemia. Despite widespread adoption of a cut-off of < 0.8 MoM in the published literature for the polycythemic fetus in TAPS, this is based upon minimal evidence, with unknown sensitivity and specificity. We recommend caution in excluding TAPS based purely upon the absence of a reduced MCA-PSV.

Automated cardiac time interval measurement for Modified Myocardial Performance Index calculation of right ventricle

The Modified Myocardial Performance Index (Mod-MPI) has sparked great interest as a parameter for fetal cardiac function assessment. However, measurement of this index requires expertise and its clinical application might be limited, owing to its poor repeatability. Research groups have been investigating left Mod-MPI (that is, Mod-MPI from left ventricle valve events), and an automated algorithm has been developed for left Mod-MPI calculation in our previous study. Right MPI is also important as it becomes abnormal earlier than left MPI in some pathologies; however, for use across the gestational age spectrum, it requires two-image acquisition. This paper presents an automated method to detect valve movements during atrioventricular outflow and ventricular inflow and to further calculate the time intervals required for right MPI calculation. Ninety pulsed-wave Doppler ultrasound images of the right ventricle in fetuses, forty-five showing outflow and forty-five inflow, were analyzed to automatically detect the valve clicks generated by tricuspid valve movement in inflow waves, and pulmonary valve movement in outflow waves. The morphological characteristics of waves were combined with intensity information to locate clicks. This automated method can detect valve movement events with a high positive predictive value (96.20-98.96%) and sensitivity (97.95-100.00%), using manual annotation from an expert ultrasonographer as the gold standard for evaluation.

Ultrasound (in)accuracy: it's in the formulae not in the technique - assessment of accuracy of abdominal circumference measurement in term pregnancies

Introduction: Fetal abdominal circumference (AC) is utilised in calculations for the estimation of fetal weight (EFW) and has been proposed as a method of monitoring diabetic pregnancies. We evaluated true ultrasound accuracy by comparing fetal AC biometry with neonatal anthropometry and compared this with standard ultrasound estimations of fetal weight.

Methods: A prospective observational study was performed at a tertiary referral centre. Women who were having their confinement of a term, singleton gestation either by induction of labour or elective caesarean section from 2009–2011 were approached to participate. An ultrasound was performed within 24 hours of delivery measuring the biometric parameters of AC, head circumference (HC), biparietal diameter and femur length. Following delivery the AC, HC and birthweight were measured on the neonate.

Results: Fifty‐two patients were enrolled in the study with data collected from 50. Mean AC measurement was 35.1 ± 2.1 cm and birth weight was 3596 ± 517 g. A Bland‐Altman plot was used to compare the two AC measurements with the 95% limits of agreement ranging from −2.33–4.69 cm around a mean difference of 1.2 cm. Mean percentage error was 5.0% and 6.2% for the AC and HC measurements respectively, in comparison with percentage errors of 7.0–13.8% for estimation of fetal weight (EFW) from 27 formulae.

Conclusions: Sonographic AC measurement is accurate in term pregnancies, with a percentage error less than HC or EFW. Perceptions of ultrasound inaccuracy may relate to the application of formulae rather than the ultrasound technique itself. Fetal surveillance using serial AC measurement has been proposed, in particular monitoring of diabetic pregnancies and in such a group AC may be easier and faster to obtain and more meaningful than EFW.

Importance of Pulse Repetition Frequency Adjustment for 3- and 4-Dimensional Power Doppler Quantification

OBJECTIVES

To determine the influence of the pulse repetition frequency (PRF) and wall motion filter on the 3-dimensional (3D) power Doppler vascularization-flow index (VFI) and volumetric pulsatility index (PI) obtained from spatiotemporal image correlation (STIC) data sets acquired from a common carotid artery of a healthy participant.

METHODS

We acquired 11 STIC data sets, 1 for each PRF value ranging from 0.6 to 9.0 kHz. Vascularization-flow index and volumetric PI values were determined from the 440 static 3D data sets contained in these STIC data sets. Additionally, 3 sets of radio-frequency data were acquired for offline processing of different wall motion filter values for PRF values of 0.6, 3.3, and 10 kHz.

RESULTS

We constructed VFI curves and observed 2 patterns: a flattened pattern with a low PRF and a triphasic pattern with a high PRF, correlating with the known pulsed wave Doppler profile of this vessel. Volumetric PI values were around 0 for low PRF settings and increased with increasing PRF. Analysis of the radiofrequency data showed that increasing wall motion filter values gradually filtered out the low-velocity power Doppler signals while retaining the higher-velocity ones, allowing the distinction of integrated power Doppler signal velocity throughout the cardiac cycle.

CONCLUSIONS

We conclude that the PRF and wall motion filter dramatically influence 3D power Doppler indices and the volumetric PI, and the use of PRF values in which minimum VFI values are measured during the diastolic phase in the spectral Doppler wave may validate the use of the volumetric PI.

Monitoring intrahepatic cholestasis of pregnancy using the fetal myocardial performance index: a cohort study

OBJECTIVE

To investigate use of the fetal myocardial performance index (MPI) in assessing intrahepatic cholestasis of pregnancy (ICP).

METHODS

This was a cohort study including cross-sectional and longitudinal data from 31 women with ICP recruited from June 2012 to March 2014. Fetal left, right and delta MPI (LMPI, RMPI and DMPI), and routine measures of fetal growth and wellbeing, were obtained at each ultrasound examination. Results were evaluated with respect to gestational age (GA)-adjusted reference intervals, level of maternal serum bile acid (SBA) and fetal outcome. Lower SBA (≥ 7.5 and < 40 μmol/L) and high SBA (≥ 40 μmol/L) subgroups of cases were defined for the analysis.

RESULTS

A total of 51 ultrasound examinations were performed in 33 fetuses. The mean LMPI, and means of its isovolumetric relaxation time (IRT) and isovolumetric contraction time (ICT) components were significantly higher in all subgroups of cases of ICP relative to the normal reference mean. Considering only the first examination in each case of ICP, IRT was significantly more prolonged in the high SBA group (n = 10) in comparison to the lower SBA group (n = 23) (52.7 ± 8.0 ms vs 47.3 ± 4.8 ms, P = 0.02), and both IRT (r = 0.538, P = 0.001) and LMPI (r = 0.367, P = 0.036) were significantly correlated with SBA concentration. The proportion of high SBA cases with LMPI, RMPI or DMPI > 2 SD above the GA-adjusted reference mean was not significantly greater than for the lower SBA group. On analysis of all data from those cases with more than one examination, no significant correlation was found between SBA concentration and any of the MPI variables.

CONCLUSIONS

LMPI values increase above the population GA-adjusted mean in cases of ICP, particularly amongst women with higher SBA. A significant correlation between IRT and LMPI at initial examination and increasing SBA concentration was found. A future multicenter prospective study may clarify the prognostic utility of MPI in ICP.

Pregnancy outcomes before and after institution of a specialised twins clinic: a retrospective cohort study

BACKGROUND

Although specialised clinics for multiple pregnancies are recommended by several Obstetrics and Gynaecology governing bodies, studies examining outcome before and after introduction of such clinics remain few, were performed predominantly in North America in the 1990s, and either amongst dichorionic twin pregnancies only or where chorionicity was not specified. Our objective, in the modern setting with twins of known chorionicity, was to compare maternal and neonatal outcomes of twin pregnancies before and after commencement of a consultant-led, multidisciplinary twins clinic (TC).

METHODS

Retrospective cohort study of 513 women, with birth of twins at ≥20 weeks' gestation, January 2007 to November 2011, at a metropolitan tertiary maternity hospital, Sydney, Australia. Demographic, pregnancy, and outcome data were obtained from hospital databases. Women receiving TC care (2009-2011) were compared to those receiving general antenatal clinic (ANC) care (2007-2010) and private care (2009-2011). Other models of care were excluded. Main outcome measures were total maternal inpatient stay, mode of birth, gestational age at birth, and neonatal nursery admission.

RESULTS

286 women were included in the main analyses: 84 attended ANC, 101 TC, and 101 a private obstetrician. TC women had similar demographics to ANC women and were slightly younger than private patients. TC women had lower Caesarean section rates (55% vs. 70% ANC and 76% private, p = 0.008) and fewer late preterm (34 + 0-36 + 6 weeks) births, (26%TC vs. 44% ANC and 41% private, p < 0.001). Median maternal inpatient stay was shorter in TC than ANC (7 vs. 8 days, p = 0.009) and similar to private (7 days). Nursery admission rates were higher in private patients (67% vs. 49% ANC and 47% TC, p = 0.001) and average birthweight lower (2283 g vs. 2501 g ANC and 2496 g TC, p < 0.001).

CONCLUSIONS

Within a single centre, maternal and neonatal twin pregnancy outcomes varied significantly by model of care. Introducing a specialised twins clinic in our setting decreased Caesarean section rates, late preterm birth, and inpatient stay compared to ANC.

Why such differing stances? A review of position statements on home birth from professional colleges

Despite low rates of home birth throughout most Western countries, the topic generates considerable debate. This is reflected by the differing positions on home birth adopted by professional colleges representing obstetricians and midwives. We reviewed position statements of midwifery and obstetric colleges in the UK, USA, Australia, New Zealand, and Canada to explore how the same body of research evidence leads to different positions. Aside from a joint statement from the UK we found widely differing stances, reflecting traditional midwifery perspectives of birth as a physiological process versus obstetric perspectives of potential pathology. We feel the differences in position statements are largely the end product of significant confirmatory bias.

TWEETABLE ABSTRACT

Review of organisational position on home birth suggests bias in literature interpretation.

The Fetal Modified Myocardial Performance Index: Is Automation the Future?

The fetal modified myocardial performance index (Mod-MPI) is a noninvasive, pulsed-wave Doppler-derived measure of global myocardial function. This review assesses the progress in technical refinements of its measurement and the potential for automation to be the crucial next step. The Mod-MPI is a ratio of isovolumetric to ejection time cardiac time intervals, and the potential for the left ventricular Mod-MPI as a tool to clinically assess fetal cardiac function is well-established. However, there are wide variations in published reference ranges, as (1) a standardised method of selecting cardiac time intervals used in Mod-MPI calculation has not been established; (2) cardiac time interval measurement currently requires manual, inherently subjective placement of callipers on Doppler ultrasound waveforms; and (3) ultrasound machine settings and ultrasound system type have been found to affect Mod-MPI measurement. Collectively these factors create potential for significant inter- and intraobserver measurement variability. Automated measurement of the Mod-MPI may be the next key development which propels the Mod-MPI into routine clinical use. A novel automated system of Mod-MPI measurement is briefly presented and its implications for the future of the Mod-MPI in fetal cardiology are discussed.

Is There a Measurable Difference between the Left and Right Modified Myocardial Performance Indices, and Does This Change to Reflect Unilateral Myocardial Dysfunction in Pathology?

Introduction: Fetal cardiac dysfunction may manifest itself unilaterally as right and left ventricles differing in design, function and load, measurable as differing in myocardial performance indices (MPIs). We wished to define this difference (‘delta-MPI' or DMPI), present its normal range and pilot its use in pathological pregnancy. Material and Methods: Prospective cross-sectional study of 324 normal singleton fetuses (16-38 weeks of gestation). Left and right modified MPI (LMPI and RMPI) were performed during a single examination using the ‘peak' valve click technique. Thirty-seven pathological singleton and monochorionic diamniotic twin pregnancies were compared as pilot data. Results: Modified MPIs (mean ± SD) were 0.45 ± 0.06 (LMPI) and 0.47 ± 0.09 (RMPI), being similar at 18 weeks' gestation with DMPI increasing slightly throughout pregnancy (0.02 ± 0.08). Both singleton intrauterine growth restriction (IUGR) and recipient twin-twin transfusion syndrome (TTTS) showed significantly elevated RMPI, LMPI and DMPI, most pronounced for DMPI (450 and 500% increase, respectively; p < 0.01). DMPI acquisition rates were 83.3% normal and 87.0% pathological. Discussion: We demonstrate for the first time differing intrafetal LMPI and RMPI in a large gestational cohort, with this difference increasing with gestational age. Pilot data confirm the potential for DMPI as a tool to assess unilateral myocardial function in singleton IUGR and recipient twins in TTTS, and further studies are under way to evaluate its clinical utility.

The (Pulsed-Wave) Doppler Fetal Myocardial Performance Index: Technical Challenges, Clinical Applications and Future Research

Functional cardiovascular assessment is becoming an increasingly important tool in the study of fetal pathology. The myocardial performance index (MPI) is a parameter measuring global myocardial function. Since its introduction, several studies have proposed methods to improve its reproducibility and have constructed normative reference ranges. Fetal heart evaluation using the MPI is technically challenging, requiring specific training and expertise, and a consensus has yet to be reached on the method of delineating the time periods used to calculate the index. Despite these limitations, it has been shown to be a useful and highly sensitive parameter of dysfunction in a number of fetal pathologies. Further research is warranted into the effect of pathology on MPI, parameters of unilateral cardiac strain that utilise MPI, and automation of the MPI to encourage incorporation of the MPI as a useful tool in clinical practice.

Automated fetal cardiac valve movement detection for modified myocardial performance index calculation

The Modified Myocardial Performance Index (Mod-MPI) is becoming an important index in fetal cardiac function evaluation. However, the current method for Mod-MPI calculation can be time-consuming and demonstrates poor inter-operator repeatability. This paper presents an automated method for detecting the opening and closing events of fetal cardiac valves with the aim of automating the Mod-MPI calculation. Fifty-four Doppler ultrasound images, showing blood inflow and outflow for the left ventricle, are analyzed to attempt to automatically detect the timings of a total of 905 opening and closing events for both aortic and mitral valves. Timings are found according to the morphological characteristics of waveforms as well as intensity information of images. The proposed method can detect the four valve movement events with high sensitivity (95.60-98.64%) and precision (96.85-100.00%). Results are verified by comparison with manual annotation of same images from an expert.

Long term developmental outcomes of pre-school age children following laser surgery for twin-to-twin transfusion syndrome

BACKGROUND

Laser therapy is now a well recognised treatment for twin-to-twin transfusion syndrome (TTTS). We investigated the early childhood neurodevelopmental outcome of children post laser treatment for TTTS in our centre.

METHODS

Children of women who had laser therapy for TTTS between March 2006 and June 2008 were assessed at 30-69 months of age with WPPSI-III and a general health questionnaire. Major neurodevelopmental impairment (NDI) was reported as IQ<70 or cerebral palsy (CP). Borderline cognitive impairment was defined by IQ 70-79.

RESULTS

Amongst the 37 pregnancies treated, 62 infants were discharged home and the overall foetal survival rate was 84%. A total of 50 children (84%) from 31 pregnancies were assessed. Average age at assessment was 47 months. Two children with late treatment of congenital hypothyroidism were excluded. The majority of pregnancies were Quintero Stage III (74%). There was a significant trend for worse outcome with higher Quintero stage. The average gestational age at birth was 32 weeks. The majority (39, 78%) of children were found to be neurodevelopmentally normal; 9 (18%) had borderline cognitive development; and 2 (4%) had a major NDI, including one with cerebral palsy (2%).

CONCLUSIONS

There was a modest level of neurocognitive impairment post laser therapy for TTTS, mainly borderline cognitive development, lesser so major NDI. There was a low incidence of cerebral palsy. Routine developmental and neurological follow-up of these children is recommended.

A technique for the estimation of fractional moving blood volume by using three-dimensional power Doppler US

PURPOSE

To (a) demonstrate an image-processing method that can automatically measure the power Doppler signal in a three-dimensional ( 3D three-dimensional ) ultrasonographic (US) volume by using the location of organs within the image and (b) compare 3D three-dimensional fractional moving blood volume ( FMBV fractional moving blood volume ) results with commonly used, unstandardized measures of 3D three-dimensional power Doppler by using the human placenta as the organ of interest.

MATERIALS AND METHODS

This is a retrospective study of scans obtained as part of a prospective study of imaging placental biomarkers with US, performed with ethical approval and written informed consent. One hundred forty-three consecutive female patients were examined by using an image-processing technique. Three-dimensional FMBV fractional moving blood volume was measured on the vasculature from the uteroplacental interface to a depth 5 mm into the placenta by using a normalization volume 10 mm outside the uteroplacental interface and compared against the Virtual Organ Computer-aided AnaLysis ( VOCAL Virtual Organ Computer-aided AnaLysis ; GE Healthcare, Milwaukee, Wis) vascularization flow index ( VFI vascularization flow index ). Intra- and interobserver variability was assessed in a subset of 18 volumes. Wilcoxon signed rank test and intraclass correlation coefficients were used to assess measurement repeatability.

RESULTS

The mean 3D three-dimensional FMBV fractional moving blood volume value ± standard deviation was 11.78% ± 9.30 (range, 0.012%-44.16%). Mean VFI vascularization flow index was 2.26 ± 0.96 (range, 0.15-6.06). Linear regression of VFI vascularization flow index versus FMBV fractional moving blood volume produced an R(2) value of 0.211 and was significantly different in distribution (P < .001). Intraclass correlation coefficient analysis showed higher FMBV fractional moving blood volume values than VFI vascularization flow index for intra- and interobserver variability; intraobserver values were 0.95 for FMBV fractional moving blood volume (95% confidence interval [ CI confidence interval ]: 0.90, 0.98) versus 0.899 for VFI vascularization flow index (95% CI confidence interval : 0.78, 0.96), and interobserver values were 0.93 for FMBV fractional moving blood volume (95% CI confidence interval : 0.82, 0.97) versus 0.67 for VFI vascularization flow index (95% CI confidence interval : 0.32, 0.86).

CONCLUSION

The extension of an existing two-dimensional standardized power Doppler measurement into 3D three-dimensional by using an image-processing technique was shown in an in utero placental study. Three-dimensional FMBV fractional moving blood volume and VFI vascularization flow index produced significantly different results. FMBV fractional moving blood volume performed better than VFI vascularization flow index in repeatability studies. Further studies are needed to assess accuracy against a reference standard.

Complicated multiple pregnancy referral, treatment and outcomes at the NSW Fetal Therapy Centre

Objectives: To determine the indications for referral, sonographic workload, diagnoses and outcomes of women with a multiple pregnancy referred to the New South Wales Fetal Therapy Centre (NSW FTC). Methods: Retrospective cohort study of twin and higher order multiple (HOM) pregnancies referred to the NSW FTC at the Royal Hospital for Women (RHW) Department of Maternal Fetal Medicine (MFM), Sydney from January 2007 to December 2009.

Results: There were 176 twin pregnancies (138 monochorionic diamniotic, 29 dichorionic diamniotic and nine monoamniotic), and 26 HOMs referred (23 triplet and three quadruplet pregnancies). Indications for referral were: twin to twin transfusion syndrome (TTTS) 103 women, fetal anomaly 31 women, intrauterine growth restriction (IUGR) 12 women, serial surveillance of twins or HOM 37 women, and fetal reduction of HOM (nine women). In 80.2% the pathological referral diagnosis was confirmed. The average number of ultrasounds was five (range 1–24), with 90 women (45%) receiving invasive therapy. Thirty‐five percent (71) of referrals were from outside Sydney, including eight interstate and 11 overseas referrals. Two‐thirds of out of area referrals were able to return to their referral hospital for birth: 95 women (47%) delivered at RHW.

Conclusion: TTTS was the most common reason for referral, with a high concordance between referral and initial diagnosis. RHW accepted a large number of out of area referrals, in keeping with its role as the NSW FTC. Twin and HOM pregnancy referrals represent a significant workload for the 5 department, with many women also requiring invasive therapy.

Selection of the sub-noise gain level for acquisition of VOCAL data sets: a reliability study

This study was aimed at assessing the intra-observer and inter-observer repeatability of selecting the sub-noise gain (SNG) level when acquiring placental volumes with 3-D power Doppler for analysis using virtual organ computer-aided analysis (VOCAL). Sixty women with uncomplicated singleton pregnancies between 20 and 38 wk of gestation were recruited. Two women were excluded for flash artifact noted during image analysis. Two blinded observers independently adjusted gain to their perceived SNG level before acquiring a static 3-D volume of the placenta at the cord insertion; observers alternated after each acquisition until each had acquired two volumes. A single observer operated the probe at all times. During offline analysis, SNG levels were recorded and VOCAL indices were calculated. SNG exhibited excellent intra-observer and inter-observer reliability. Intra-observer intra-class correlation coefficients (95% confidence intervals) were 0.98 (0.97-0.99) and 0.98 (0.98-0.99) for observers 1 and 2, respectively. The inter-observer intra-class correlation coefficient was 0.96 (0.93-0.98). Despite its perceived inherent subjectivity, the excellent intra-class correlation coefficients obtained in this study support SNG as a promising tool for future research using 3-D power Doppler.

Randomised controlled trials and clinical maternity care: moving on from intention-to-treat and other simplistic analyses of efficacy

BACKGROUND

The obstetrical literature is dominated by Randomised Controlled Trials (RCTs), with the vast majority being analysed using an intention-to-treat (ITT) approach. Whilst this approach may reflect well the consequence of assignment to therapy and hence the 'trialists'perspective', it may fail to address the consequence of actually receiving therapy (the patient's perspective).

DISCUSSION

This review questions the ubiquitous adherence to the ITT approach, and gives examples of where this may have misled the maternity care professions. It gives an overview of techniques to overcome potential deficiencies in result presentation, using method effectiveness models such as 'Per Protocol' (PP) or 'As-Treated' (AT) that may give more accurate clinical meaning to the presentation of obstetrical results. It then proceeds to cover the added benefits, considerations and potential pitfalls of the use of Instrumental Variable (IV) models in order to better reflect the clinical context.

SUMMARY

While ITT may achieve statistical purity, it frequently fails to address the true clinical or patient's perspective. Though more complex and potentially beset by problems of their own, alternative methods of result presentation may better serve the latter aim. Each of the other methods may rely on untestable assumptions and therefore it is wisest that study results are presented in multiple formats to allow for informed reader evaluation.

Inapplicability of fractional moving blood volume technique to standardize Virtual Organ Computer-aided AnaLysis indices for quantified three-dimensional power Doppler

OBJECTIVE

To determine whether the technique of fractional moving blood volume (FMBV) is applicable to Virtual Organ Computer-aided AnaLysis II (VOCAL II™)-based indices to quantify three-dimensional power Doppler ultrasound (3D-PDU) by investigating the effect of gain level on the indices measured at a possible reference point for standardization.

METHODS

Ten women with singleton pregnancy between 33+3 and 37+5 weeks' gestation were recruited. The optimal position for 3D acquisition of cord insertion into the placenta was identified and static 3D-PDU volumes were acquired using consistent machine configurations. Without moving the probe or the participant changing position, successive 3D volumes were stored at -3, -5, -7 and -9 dB and at the individualized sub-noise gain (SNG) level. Volumes were excluded if flash artifact was present, in which case all five volumes were reacquired. Using 4D View software, the cord insertion was magnified and the smallest sphere possible was used to measure vascularization index (VI), flow index (FI) and vascularization flow index (VFI). The associations between VOCAL indices and gain level were assessed using Pearson's correlation coefficient.

RESULTS

VOCAL indices for cord insertion correlated poorly with gain level, whether fundamental or relative to SNG level (R(2) = 0.07 and 0.04, respectively). VI was consistently 100% and mean FI and VFI were 99.5 (SD, 0.57), with all values > 97 irrespective of gain level.

CONCLUSIONS

Whilst previous work has shown that gain correlates well with placental tissue VOCAL indices, the correlation between gain level and VOCAL indices in an area of 100% vascularity at the cord insertion is poor. Regions of 100% vascularity appear to be artificially assigned a value approaching 100% for all VOCAL indices irrespective of gain level. This precludes using the technique of VOCAL indices from large vessels to standardize power Doppler measurements and the FMBV index is therefore not applicable to image analysis using VOCAL.

Collaboration in maternity care is achievable and practical

BACKGROUND

Enhancing collaboration has been highlighted as a marker for future success in maternity care, although this suggestion comes with little methodological guidance. This study assessed the efficacy of a collaborative partnership between obstetric doctors and midwives providing Midwifery Group Practice (MGP) care.

METHODS

A retrospective analysis was undertaken with notes from weekly case review meetings held between the obstetricians and midwives over a 12-month period; audio recordings and a prospective analysis of 16 meetings with verbal contributions of the different professions; the number and types of cases discussed and referred, medical records kept at these meetings and a professional satisfaction questionnaire. Consistency of care was measured against the Australian National Midwifery Guidelines for Consultation and Referral.

RESULTS

Of the 337 women booked with MGP, 50% were discussed at least once. Of these, 35% were referred for consultation with an obstetrician. Women as 'Patients' were most commonly discussed, followed by educational discussions and anecdotes with equal verbal contributions from midwives and doctors. Plans for each case were recorded 97% of the time, and adhered to 90% of the time. A high level of consistency of care between similar cases (75% of the time) and with the consultation and referral guidelines (85% of the time) were achieved. Professional satisfaction with this model of care rated highly for both groups.

CONCLUSION

Inter-professional collaboration between midwifery and obstetric staff is highly attainable within this model of care. This study reinforces the effectiveness of collaboration in the MGP model of care for women of all risk levels and should encourage other maternity care providers to consider adopting this collaborative model.