Quantitative assessment of placental vasculature and placental volume in normal pregnancies with the use of 3D Power Doppler

Does a Caesarean Section Scar Affect Placental Volume, Vascularity and Localization?

Caesarean section is associated with an increased risk of abnormal placental implantation and adverse pregnancy outcomes in subsequent pregnancies. Besides the placenta accrete spectrum, only a few of the previous studies focused on other placental development alterations in the scarred uterus. We assessed placental development deviations in the uterus with a Caesarean section scar by evaluating placental volume (PV) and vascular flow indexes. From 1 January 2021 until 31 March 2022, placental volumes and vascularization indexes (VI, FI, VFI) were prospectively measured by 3D power Doppler and VOCAL techniques in 221 patients attending the first trimester screening program. We also calculated the placental quotient to standardize PV to the gestational age. No statistically significant differences in the values of placental volume, placental quotient and placental vascularization indexes were detected between women with previous Caesarean section delivery or women with vaginal delivery. FI was significantly lower in nulliparous in the first trimester. The results of our study suggest that 3D placental evaluation was not able to detect placental development alteration in the uterus with a Caesarean section scar. Future research needs to verify whether 3D power Doppler and Vocal techniques can provide more information if used in an earlier gestational age.

Ultrasound evaluation of the radial artery in young adults - A pilot study

The radial artery is a vessel frequently used in various medical procedures which carry a risk of complications. One such method used to minimize the number of complications is a profound knowledge of the artery's diameter, which allows for appropriate selection of an instrument to use for puncture. The purpose of this study is to determine the diameter of the radial artery and its depth from the skin surface in young adults.

MATERIAL AND METHODS

96 volunteers participated in the study. The average age of the volunteers was 20.43 years. All participants underwent a B-mode ultrasonography to measure the distal radial artery's diameter. Certified anthropometric instruments were used to determine the relation between the artery diameter and the selected basic anthropometric parameters.

RESULTS

The mean right arterial diameter for the entire examined population at the level of the styloid process was mean 1.42 (SD 0.26) mm and its distance to the skin was mean 4.00 (SD1.20) mm. Statistical analysis revealed the presence of moderate positive relationship between the diameter of the radial artery and body weight and between the diameter of the radial artery and BMI. A weak correlation between the artery diameter and the width of the wrist was also present.

CONCLUSION

In the present work, we aimed to determine the dimensions of the distal section of the radial artery in young people free from symptoms of cardiovascular diseases. The obtained initial study results advise selecting instruments for vascular puncture individually, with special attention paid to slender people with slim wrists.

Feasibility of three dimensional power Doppler ultrasonography methods to assess placental perfusion

OBJECTIVES

Given the crucial role of the placenta in establishing a healthy pregnancy, reliable non-invasive methods to measure placental perfusion are desirable. The aim of this study is to determine the reproducibility and potential bias in different three-dimensional power Doppler (3DPD) methods assessing placenta perfusion.

METHODS

Ten singleton pregnancies around 16 weeks of gestation, with an anteriorly located placenta and centrally inserted umbilical cord were included in this study. Eight different combinations of a specific placental sweep and sonobiopsy method were used to evaluate placental perfusion. Vascularization index (VI), flow index (FI) and vascularization-flow index (VFI) were determined offline using the 4D-view program. Reproducibility and repeatability of the methods, expressed as correlation coefficients and Bland-Altman mean differences, were calculated. Differences between sampling methods were analyzed using t-test or Mann-Whitney U test.

RESULTS

Intra- and inter-class correlation coefficient (CC) was highest when using a spherical centrally placed sonobiopsy of 2 cm³ in a whole placenta sweep (method 1; IntraCC VI 0.985, FI 0.769, VFI 0.993, InterCC VI 0.986, FI 0.784, VFI 0.987). Overall, intraCCs were higher compared to interCCs. Lowest mean differences in VI and FI were found comparing spherical to manual sonobiopsies, whereas the mean differences in VFI were lowest when comparing central versus peripheral located sonobiopsies. Comparing the three vascular indices, best median intra- and interCC and lowest mean differences were found for VFI.

CONCLUSIONS

Three dimensional placental vascularization analysis showed best reproducibility using whole placental sweep volume and centrally located, spherical sonobiopsy of 2 cm³.

Maternal Utero-Placental Perfusion Discordance in Monochorionic-Diamniotic Twin Pregnancies with Selective Growth Restriction Assessed by Three-Dimensional Power Doppler Ultrasound

Background

The aim of this study was to assess the correlation between selective growth restriction (sGR) and co-twin utero-placental perfusion discordance by using three-dimensional power Doppler (3DPD).

Material/Methods

We prospectively recruited 60 sGR and 64 normal monochorionic-diamniotic (MCDA) twin pregnancies. Vascularization index (VI), flow index (FI), and vascularization flow index (VFI) were assessed by 3DPD, while umbilical artery pulsatility index (UA-PI), middle cerebral artery peak systolic velocity (MCA-PSV), pulsatility index (MCA-PI), and cerebroplacental ratio (CPR) were assessed by conventional Doppler imaging.

Results

In sGR co-twins, the VI, FI, VFI, MCA-PI, and CPR were significantly lower, while the UA-PI and MCA-PSV were significantly greater, in the smaller fetuses compared with the larger fetuses; significant differences were also observed in the VI, FI, VFI, CPR, and UA-PI in normal co-twins. Compared with the appropriately grown twins, the discordances of the VI, FI, VFI, UA-PI, MCA-PI, and CPR were increased in the sGR cohort. The discordances of the VI, FI, VFI, UA-PI, MCA-PI, and CPR were associated with birthweight discordance, and the FI discordance and CPR discordance were independently associated with sGR. The combination of the FI and CPR discordance showed a higher predictive accuracy for sGR, with an area under the ROC curve of 0.813, and a sensitivity and specificity of 68.33% and 85.94%, respectively.

Conclusions

MCDA twin pregnancies with birthweight discordance presented utero-placental perfusion deterioration assessed by 3DPD prior to sGR diagnosis. Co-twin utero-placental perfusion discordance was significantly correlated with growth discordance, and this correlation was more predictive of sGR when 3DPD was combined with conventional Doppler imaging.

Gestation-Specific Changes in the Anatomy and Physiology of Healthy Pregnant Women: An Extended Repository of Model Parameters for Physiologically Based Pharmacokinetic Modeling in Pregnancy

BACKGROUND

In the past years, several repositories for anatomical and physiological parameters required for physiologically based pharmacokinetic modeling in pregnant women have been published. While providing a good basis, some important aspects can be further detailed. For example, they did not account for the variability associated with parameters or were lacking key parameters necessary for developing more detailed mechanistic pregnancy physiologically based pharmacokinetic models, such as the composition of pregnancy-specific tissues.

OBJECTIVES

The aim of this meta-analysis was to provide an updated and extended database of anatomical and physiological parameters in healthy pregnant women that also accounts for changes in the variability of a parameter throughout gestation and for the composition of pregnancy-specific tissues.

METHODS

A systematic literature search was carried out to collect study data on pregnancy-related changes of anatomical and physiological parameters. For each parameter, a set of mathematical functions was fitted to the data and to the standard deviation observed among the data. The best performing functions were selected based on numerical and visual diagnostics as well as based on physiological plausibility.

RESULTS

The literature search yielded 473 studies, 302 of which met the criteria to be further analyzed and compiled in a database. In total, the database encompassed 7729 data. Although the availability of quantitative data for some parameters remained limited, mathematical functions could be generated for many important parameters. Gaps were filled based on qualitative knowledge and based on physiologically plausible assumptions.

CONCLUSION

The presented results facilitate the integration of pregnancy-dependent changes in anatomy and physiology into mechanistic population physiologically based pharmacokinetic models. Such models can ultimately provide a valuable tool to investigate the pharmacokinetics during pregnancy in silico and support informed decision making regarding optimal dosing regimens in this vulnerable special population.

Three dimensional power Doppler of the placenta and its clinical applications

The aim of this review is to discuss three dimensional (3D) power Doppler of the placenta and its clinical applications. There is a strong clinical need to develop noninvasive, simple and widely available methods of evaluating in vivo placental function to assess fetal wellbeing. While conventional ultrasound is a proven tool in the evaluation of fetal structural anomalies and health, its ability to assess placental function, especially prior to the onset of fetal compromise, is the subject of ongoing investigation. Three dimensional power Doppler has the ability to detect vascularity and blood flow with greater detail than conventional ultrasound, which has led to its investigation in preeclampsia, fetal growth restriction, and other placental vascular abnormalities. While more data are needed on the optimal imaging protocol and its predictive ability for clinical outcomes, 3D power Doppler is emerging as a promising new technology that will improve the evaluation of placental function.

Short-Term Exposure to Urban Air Pollution and Influences on Placental Vascularization Indexes

BACKGROUND

It has been widely demonstrated that air pollution can affect human health and that certain pollutant gases lead to adverse obstetric outcomes, such as preeclampsia and fetal growth restriction.

OBJECTIVES

We evaluated the influence of individual maternal exposure to air pollution on placental volume and vascularization evaluated in the first trimester of pregnancy.

METHODS

This was a cross-sectional study on low-risk pregnant women living in São Paulo, Brazil. The women carried passive personal NO₂ and O₃ monitors in the week preceding evaluation. We employed the virtual organ computer-aided analysis (VOCAL) technique using three-dimensional power Doppler ultrasound to evaluate placental volume and placental vascular indexes [vascularization index (VI), flow index (FI), and vascularization flow index (VFI)]. We analyzed the influence of pollutant levels on log-transformed placental vascularization and volume using multiple regression models.

RESULTS

We evaluated 229 patients. Increased NO₂ levels had a significant negative association with log of VI (p = 0.020 and beta = -0.153) and VFI (p = 0.024 and beta = -0.151). NO₂ and O₃ had no influence on the log of placental volume or FI.

CONCLUSIONS

NO₂, an estimator of primary air pollutants, was significantly associated with diminished VI and VFI in the first trimester of pregnancy.

Non-invasive evaluation of placental blood flow: lessons from animal models

In human obstetrics, placental vascularisation impairment is frequent as well as linked to severe pathological events (preeclampsia and intrauterine growth restriction), and there is a need for reliable methods allowing non-invasive evaluation of placental blood flow. Uteroplacental vascularisation is complex, and animal models are essential for the technical development and safety assessment of these imaging tools for human clinical use; however, these techniques can also be applied in the veterinary context. This paper reviews how ultrasound-based imaging methods such as 2D and 3D Doppler can provide valuable insight for the exploration of placental blood flow both in humans and animals and how new approaches such as the use of ultrasound contrast agents or ultrafast Doppler may allow to discriminate between maternal (non-pulsatile) and foetal (pulsatile) blood flow in the placenta. Finally, functional magnetic resonance imaging could also be used to evaluate placental blood flow, as indicated by studies in animal models, but its safety in human pregnancy still requires to be confirmed.

Reduced placental volume and flow in severe growth restricted fetuses

OBJECTIVES

To evaluate placental volume and vascular indices in pregnancies with severe fetal growth restriction and determine their correlations to normal reference ranges and Doppler velocimetry results of uterine and umbilical arteries.

METHODS

Twenty-seven fetuses with estimated weights below the 3rd percentile for gestational age were evaluated. Placental volume and vascular indices, including vascularization, flow, and vascularization flow indices, were measured by three-dimensional ultrasound using a rotational technique and compared to a previously described nomogram. The observed-to-expected placental volume ratio for gestational age and observed-to-expected placental volume ratio for fetal weight were calculated. Placental parameters correlated with the Doppler velocimetry results of uterine and umbilical arteries.

RESULTS

The mean uterine artery pulsatility index was negatively correlated with the observed-to-expected placental volume ratio for gestational age, vascularization index and vascularization flow index. The observed-to-expected placental volume ratio for gestational age and observed-to-expected placental volume ratio for fetal weight and vascularization index were significantly lower in the group with a bilateral protodiastolic notch. No placental parameter correlated with the umbilical artery pulsatility index.

CONCLUSIONS

Pregnancies complicated by severe fetal growth restriction are associated with reduced placental volume and vascularization. These findings are related to changes in uterine artery Doppler velocimetry. Future studies on managing severe fetal growth restriction should focus on combined results of placental three-dimensional ultrasound and Doppler studies of uterine arteries.