Nia W. Jones

Maternal Smoking during Pregnancy and Fetal Organ Growth: A Magnetic Resonance Imaging Study

Objective To study whether maternal cigarette smoking during pregnancy is associated with alterations in the growth of fetal lungs, kidneys, liver, brain, and placenta. Design A case-control study, with operators performing the image analysis blinded. Setting Study performed on a research-dedicated magnetic resonance imaging (MRI) scanner (1.5 T) with participants recruited from a large teaching hospital in the United Kingdom. Participants A total of 26 pregnant women (13 current smokers, 13 non smokers) were recruited; 18 women (10 current smokers, 8 nonsmokers) returned for the second scan later in their pregnancy. Methods Each fetus was scanned with MRI at 22–27 weeks and 33–38 weeks gestational age (GA). Main outcome measures Images obtained with MRI were used to measure volumes of the fetal brain, kidneys, lungs, liver and overall fetal size, as well as placental volumes. Results Exposed fetuses showed lower brain volumes, kidney volumes, and total fetal volumes, with this effect being greater at visit 2 than at visit 1 for brain and kidney volumes, and greater at visit 1 than at visit 2 for total fetal volume. Exposed fetuses also demonstrated lower lung volume and placental volume, and this effect was similar at both visits. No difference was found between the exposed and nonexposed fetuses with regards to liver volume. Conclusion Magnetic resonance imaging has been used to show that maternal smoking is associated with reduced growth of fetal brain, lung and kidney; this effect persists even when the volumes are corrected for maternal education, gestational age, and fetal sex. As expected, the fetuses exposed to maternal smoking are smaller in size. Similarly, placental volumes are smaller in smoking versus nonsmoking pregnant women.

Utero-Placental Haemodynamics in the Pathogenesis of Pre-Eclampsia

Pre-eclampsia is associated with insufficient adaptations of spiral arteries which theoretically alter haemodynamics within the intervillous space. Such changes could damage the syncytiotrophoblast and release factors which instigate maternal endothelial dysfunction. We tested this hypothesis using an in vitro dual perfusion model of the human placenta, representing putative changes in flow arising from these spiral artery maladaptations. Whilst fetal-side flow rates remained constant (6 ml/min) perfusion rates on the maternal side were increased from 14 ml/min to 45 ml/min. As well as increasing placental derived intervillous hydrostatic pressures, and changes in flow dynamics observed by colour Doppler, these elevated flow rates resulted in morphologic damage, vacuolation and shedding of the syncytiotrophoblast, focal features previously defined in pre-eclampsia. The collected maternal perfusates recovered under high flow conditions also contained significantly elevated levels of biochemical markers of syncytial damage, including lactate dehydrogenase, alkaline phosphatase and human chorionic gonadotrophin. There were also significant elevations in chemokines GROalpha and RANTES, compared with the low flow perfusions. The soluble components of the maternal high flow rate perfusions decreased the number and proliferation of HUVECs after 24h exposure. These results could not be attributed to GROalpha or RANTES alone or in combination. This study provides evidence that alterations in intervillous flow have the potential to influence both the integrity of the syncytiotrophoblast and the liberation of potentially pathogenic soluble factors. This therefore offers a putative link between utero-placental maladaptations in pregnancy and the vascular endothelial complications of pre-eclampsia.

Methodological considerations for the correct application of quantitative three‐dimensional power Doppler angiography

We were interested to read the paper by Guiot et al. entitled ‘Is three-dimensional power Doppler ultrasound useful in the assessment of placental perfusion in normal and growth-restricted pregnancies?’ in the February edition of the White Journal1. The authors used ‘3D power Doppler ultrasound indices [for] the assessment of placental perfusion’ and studied the relationship of these indices to ‘gestational age (GA), placental position, and umbilical artery Doppler FVW [flow velocity waveform] patterns in normal and IUGR [intrauterine growthrestricted] pregnancies’. We have some methodological queries and would also like to comment on several statements made about the three-dimensional (3D) vascular indices and their purported relationship to true blood flow characteristics. The authors make many assumptions and several factually incorrect statements about quantitative threedimensional power Doppler angiography. They state that ‘even very small blood movements within the investigated volume can be detected by a combination of power and color Doppler sonography, and their impact in the given volume, representing the overall perfusion, is evaluated by indices computed by built-in algorithms’. Movement of blood, or any fluid for that matter, does not result in a Doppler signal. It is the erythocytes within the blood or scatterers within a fluid medium that are responsible for the Doppler shift that is represented by a color map or waveform. Blood flow and perfusion are distinct entities with differing definitions. Flow is the amount of blood passing per unit time (usually per minute) while perfusion is defined as the amount of flow in a volume of tissue per unit time and is usually measured as milliliters per minute per gram of tissue, although, since the density of most tissues is near to 1 g/mL, units of milliliters per minute per milliliter are often substituted2. The threedimensional vascular indices reported in the study are not a function of time and their quantification cannot, therefore, equate to perfusion or flow. Whilst analysis of Doppler waveforms takes into consideration the cardiac cycle it does not account for volume flow as it is a twodimensional assessment and is not a measure of perfusion either. The authors’ descriptions of the 3D vascular indices are also incorrect and therefore misleading, as they refer to the vascularization index (VI) as being representative of ‘overall perfusion’ and say that the flow index (FI) ‘evaluates the overall blood flow in the sample volume’, but both perfusion and blood flow are time-dependent parameters. The FI represents the average color value of all color voxels, so does not even remotely consider the overall blood flow. The vascularization flow index (VFI) is described as being a measure of ‘blood velocity in the same sample volume’, but power Doppler provides no velocity information and so this statement is illogical. Current opinions are that these indices are representative of the percentage of power Doppler data within the defined volume of interest (VI), the mean signal intensity of the power Doppler information (FI), and a combination of both factors, derived through their multiplication (VFI), and it has been suggested that they are representative of vascularity and flow intensity3,4. One of the aims of the study was to investigate the effect of attenuation on the 3D vascular indices, as the authors quite rightly state that ‘different placental positions require different insonation depths (and) measurements could also be dependent on this parameter’. This is not a matter for debate; power Doppler is depth-dependent and subject to attenuation. This does not require assessment as it has been shown in both in-vitro5 and in-vivo6 studies, but further research is required to develop methodologies to account for this confounding factor, which currently limits all studies other than certain gynecological ones in which the organ of interest is in close proximity to the transducer. The only way to assess vascularity and flow within different subjects is to standardize measurements by calculating an index known as the ‘fractional moving blood volume’ (FMBV), which has been shown to correlate well with true tissue perfusion7,8. Of the 3D vascular indices, the VFI is most similar to the FMBV because it shows the moving blood volume. However, it is not truly fractional as it is not standardized. The concept of comparing different sites within the same placenta is good and, to some degree, addresses the problem of attenuation, as the patient self-standardizes. However, the data presented are the overall median values for the placentae from 30 growth-restricted fetuses and 15 controls. These absolute values are meaningless without information on placental position, as the authors maintained their Doppler settings in all cases. The more posterior placentae will have had lower vascular indices as a function of increasing depth and if these were not evenly distributed amongst the two groups they should not have been compared as separate entities9. Indeed, after accounting for the distribution of the data, the mean sampling depth should have been stated and this should have been equal between the groups before any further comparisons were made. Insufficient details were provided about the Doppler settings, which should have included the power, gain, rise and persistence and reject values. One reason why the ‘intervillous flow velocity [was] below the Doppler

Evaluating the Intra- and Interobserver Reliability of Three-Dimensional Ultrasound and Power Doppler Angiography (3D-PDA) for Assessment of Placental Volume and Vascularity in the Second Trimester of Pregnancy

Three-dimensional (3-D) power Doppler angiography (3-D-PDA) allows visualisation of Doppler signals within the placenta and their quantification is possible by the generation of vascular indices by the 4-D View software programme. This study aimed to investigate intra- and interobserver reproducibility of 3-D-PDA analysis of stored datasets at varying gestations with the ultimate goal being to develop a tool for predicting placental dysfunction. Women with an uncomplicated, viable singleton pregnancy were scanned at 12, 16 or 20 weeks gestational age groups. 3-D-PDA datasets acquired of the whole placenta were analysed using the VOCAL software processing tool. Each volume was analysed by three observers twice in the A plane. Intra- and interobserver reliability was assessed by intraclass correlation coefficients (ICCs) and Bland Altman plots. At each gestational age group, 20 low risk women were scanned resulting in 60 datasets in total. The ICC demonstrated a high level of measurement reliability at each gestation with intraobserver values >0.90 and interobserver values of >0.6 for the vascular indices. Bland Altman plots also showed high levels of agreement. Systematic bias was seen at 20 weeks in the vascular indices obtained by different observers. This study demonstrates that 3-D-PDA data can be measured reliably by different observers from stored datasets up to 18 weeks gestation. Measurements become less reliable as gestation advances with bias between observers evident at 20 weeks.

Measurement of fetal fat in utero in normal and diabetic pregnancies using magnetic resonance imaging

To assess the reliability of magnetic resonance imaging (MRI) to measure fetal fat volume in utero, and to study fetal growth in women with and without diabetes in view of the increased prevalence of macrosomia in the former.

Antenatal magnetic resonance imaging versus ultrasound for predicting neonatal macrosomia: a systematic review and meta‐analysis

Fetal macrosomia is associated with an increased risk of adverse maternal and neonatal outcomes.

Evaluation of the Intraobserver and Interobserver Reliability of Data Acquisition for Three-Dimensional Power Doppler Angiography of the Whole Placenta at 12 Weeks Gestation

The aim of this study was to investigate the intra- and interobserver reproducibility of three-dimensional (3-D) power Doppler (3-DPD) data acquisition from women at 12 weeks gestation, which were then subsequently measured by a single observer. Women with an uncomplicated, viable singleton pregnancy were scanned between 12 + 0 and 13 + 6 weeks gestations with a Voluson 730 Expert. 3-DPD data were acquired of the whole placenta by two observers: the first observer captured two datasets and the second a single dataset. Each dataset was analysed using VOCAL in the A plane with 9 degree rotation steps. Eighteen low risk women were recruited with a total of 54 datasets analysed. The intraclass correlation coefficient (ICC) was highest for the vascular indices vascularisation index (VI) and vascularisation-flow index (VFI), greater than 0.75. ICC for flow index (FI) showed moderate correlation at 0.47 to 0.65. Bland Altman plots showed the most precise vascular index to be the FI (-15% to 10% for interobserver agreement). There was no bias between datasets. Prospective studies are now required to identify if this analysis tool and method is sensitive enough to recognise patients with early-onset placental dysfunction.

Changes in myometrial ‘perfusion’ during normal labor as visualized by three‐dimensional power Doppler angiography

Myometrial contractions are one of the most important aspects of effective labor. For cells within the myometrium to work efficiently they need to be well oxygenated and this requires an adequate blood supply. This study used quantitative three‐dimensional (3D) power Doppler angiography to calculate the percentage change in myometrial blood flow during a relaxation–contraction–relaxation cycle of active labor.

A Novel Technique for the Semi-Automated Measurement of Embryo Volume: An Intraobserver Reliability Study

The aim was to assess intraobserver reliability of a new semi-automated technique of embryo volumetry. Power calculations suggested 46 subjects with viable, singleton pregnancies were required for reliability analysis. Crown rump length (CRL) of each embryo was analyzed using 2-D and a 3-D dataset acquired using transvaginal ultrasound. Virtual organ computer-aided analysis (VOCAL) was used to calculate volume of gestation sac (GSV) and yolk sac (YSV) and SonoAVC (sonography-based automated volume count) was used to quantify fluid volume (FV). Embryo volume was calculated by subtracting FV and YSV from GSV. Each dataset was measured twice. Reliability was assessed using Bland-Altman plots and intraclass correlation coefficients (ICCs). Fifty-two datasets were analyzed. Median embryo volume was 1.8 cm(3) (0.1 to 8.1 cm(3)); median gestational age 7 + 4 weeks; median CRL 13 mm (2 to 29 mm). Mean difference of embryo volume measurements was 0.1cm(3) (limits of agreement [LOA] -0.3 to 0.4 cm(3)); multiples of mean (MoM) 0.38; mean difference of CRL measurements 0.3 mm (LOA -1.4 to 2.0 mm), MoM = 0.26. ICC for embryo volume was 0.999 (95%CI 0.998 to 0.999), confirming excellent intraobserver agreement. ICC for CRL was 0.996 (95%CI 0.991 to 0.998). Regression analysis showed good correlation between embryo volume and CRL (R(2) = 0.60). The new semi-automated 3-D technique provides reliable measures of embryo volume. Further work is required to assess the validity of this technique.

Fractional volume of placental vessels in women with diabetes using a novel stereological 3D power Doppler technique

OBJECTIVES In maternal diabetes the placenta is large with abnormal vascular development and increased villous volume. We used a novel stereological 3D power Doppler ultrasound technique to investigate differences in-vivo in the placental fractional volume of power Doppler signal (FrVol-PD) between women with and without diabetes. METHODS We recruited 17 pregnant women with pre-gestational diabetes and 20 controls, all with anterior placentae. Each subject had ultrasound scans (Voluson 730 Expert) every 4 weeks between 12 and 32 weeks gestation. 3D power Doppler data were acquired and the placenta manually outlined using VOCAL (4D View). Power Doppler signal within the resultant volume was counted in a 3D manner adapting the random but systematic techniques used in stereology. RESULTS Subjects were of similar age, BMI and parity. From 16 weeks the mean (SD) placental FrVol-PD was higher in the non-diabetic than in the diabetic group: 16 weeks - 0.125 (0.03) versus 0.108 (0.03), 20 weeks - 0.144 (0.05) versus 0.104 (0.03), 24 weeks - 0.145 (0.05) versus 0.128 (0.03), 28 weeks - 0.159 (0.05) versus 0.133 (0.02) and 32 weeks - 0.154 (0.03) versus 0.123 (0.04). These differences were significant between control and diabetic subjects [F(1,35) = 4.737, p = 0.036] and across gestation [F(3,140) = 8.294, p < 0.001]. CONCLUSION Using a novel stereological-based ultrasound technique we have demonstrated the reliability of this application in the placenta. This technique shows promise for non-invasive assessment of placental function: further studies are required to identify if structural changes in a diabetic placenta are accompanied by altered function, manifest as reduced perfusion demonstrable in-vivo.