First-trimester 3D power Doppler of the uteroplacental circulation space and fetal growth restriction

B-Flow/Spatiotemporal Image Correlation M-Mode and Contrast-Enhanced/Microbubble Ultrasonography Quantification of Spiral Artery Distensibility and Placental Intervillous Perfusion in the First Trimester in a Primate Model of Impaired Spiral Artery Remodeling

OBJECTIVE

During early human pregnancy, placental trophoblasts remodel spiral arteries into distensible low-resistance vessels to promote placental perfusion. We have established a model of impaired spiral artery remodeling (SAR) by elevating estradiol levels in the first trimester of baboon pregnancy. In the present study, B-flow/spatiotemporal image correlation (STIC) M-mode ultrasonography, a non-Doppler technology for sharp rendering of vessel dimensions, was used to determine whether spiral artery distensibility was altered in SAR-suppressed baboons. Contrast-enhanced ultrasound/microbubble imaging was also performed to determine whether it detected changes in placenta intervillous space perfusion in SAR-suppressed baboons.

METHODS

The two imaging procedures were performed in the first trimester in baboons not treated or treated with estradiol to suppress SAR.

RESULTS

Spiral artery distensibility, that is, luminal diameter at systole minus diameter at diastole, and volume flow as quantified by B-flow/STIC M-mode were 26% (p = 0.03) and 55% (p = 0.059) lower, respectively, in SAR-suppressed baboons. However, placental intervillous space flow rate and video intensity plateau levels reflecting blood perfusion, quantified by contrast-enhanced ultrasound/microbubble imaging, were unaltered in SAR-suppressed baboons.

CONCLUSION

The results indicate that B-flow/STIC M-mode ultrasonography provides a non-invasive method to detect reduced distensibility and, thus, function of spiral arteries across the cardiac cycle in the first trimester in a primate model of impaired SAR. This study represents a first step in determining whether B-flow/STIC M-mode detects a similar defect in SAR early in adverse human pregnancy. This would provide an avenue to develop therapeutic modalities to prevent the devastating consequences of impaired SAR.

New insights into human functional ultrasound imaging

Ultrasound imaging is a vital tool for exploring in vivo the placental function which is essential to understand pathological phenomena such as preeclampsia or intrauterine growth restriction. As technology advances including ready availability of three-dimensional (3D) probes and novel software, new markers of placental function become possible. The objective of this review was to provide an overview of the new ultrasound markers of placental function with a focus on the potential clinical application of three-dimensional power Doppler (3DPD). A broad-free text literature search was undertaken based on human placental studies and sixty full-text studies were included in this review. Three-dimensional power Doppler is a promising technique to predict preeclampsia in the first trimester. However, the influence of external factors such as body mass index, parameter standardisation and machine settings still need to be addressed. Contrast-enhanced ultrasound is currently reserved for research, because the required injected contrast mediums are not currently approved for use in pregnancy, although the safety data is reassuring.

First trimester placental vascular indices and volume by three-dimensional ultrasound in pre-gravid overweight women

OBJECTIVES

To investigate changes of placental vascular indices and volume in pre-gravid overweight Chinese women during the first trimester using three-dimensional power Doppler ultrasound.

METHODS

This was a prospective observational study of the morphology of placentas in pre-gravid overweight (body mass index (BMI) ≥ 24 kg/m²) and non-overweight (BMI < 24 kg/m²) Chinese women during the first trimester of pregnancy. Data on placental vascular indices (vascularization index, flow index, and vascularization flow index (VFI)), placental volume, uterine artery pulsatility index (PI), and neonatal outcomes were obtained during the first trimester and analyzed. Linear regression analysis was used to evaluate confounding factors between BMI and ultrasound indices.

RESULTS

Of the 429 pregnant women enrolled, 68 (15.9%) were pre-gravid overweight. Placental VFI was significantly lower in the overweight group (p = 0.037). Conversely, placental volume was significantly larger in the overweight group (p = 0.044), and uterine artery PI was significantly higher in the overweight group (p = 0.021). After adjustments for confounding factors, there were still significant differences in placental VFI (unstandardized coefficient (B) -0.666, 95% confidence interval (CI) -1.306 - (-0.025)), placental volume (B 2.458, 95% CI 0.071-4.844), and uterine artery PI (B 0.152, 95% CI 0.030-0.274) between the two groups.

CONCLUSIONS

Placental vascular indices using three-dimensional power Doppler ultrasound can provide an insight into placental vascularization in pre-gravid overweight women in early pregnancy. Alterations in placental VFI, placental volume, and uterine artery PI occur during the first trimester in pre-gravid overweight women.

Placental Pulsatility: Quantitative Assessment of Placental Bed Vasculature by 2-Dimensional Doppler Cine Imaging

OBJECTIVES

Vascular resistance is known to be one of the determinants of pulsatile flow. This study aimed to investigate whether quantitative 2-dimensional Doppler ultrasound can capture and evaluate the pulsatility within the placental bed vasculature.

METHODS

The placental bed vasculature was imaged by directional power Doppler ultrasound. Ten-second cine clips were recorded by using standardized machine settings. A region of interest with a prominent Doppler signal in the uteroplacental interface was analyzed for the percentage of vascularity to generate a time-vascularity waveform. A vascular pulsatility index representing variation over the cardiac cycle was calculated by the ratio of the systolic-diastolic difference in vascularity to the mean vascularity. The acquisitions were repeated with 6 different pulse repetition frequencies (PRFs) and 3 wall motion filter (WMF) settings to evaluate their impact on the Doppler measurements.

RESULTS

Ten sets of cine clips were analyzed for this study. The pulsatile nature of the vascularity was readily apparent in each cine clip. The measured time-vascularity waveforms showed uniform cyclic variation in vascularity over the cardiac cycle, with systolic vascularity significantly higher than diastolic vascularity at each combination of PRF and WMF (P < .05). A gradual increase in the vascular pulsatility index was observed with an increasing PRF or WMF. Normalization of systolic-to-diastolic measurement provided a stable vascular assessment across the range of PRFs.

CONCLUSIONS

Doppler cine clips provide a dynamic representation of the placental bed vasculature and a novel analytic approach to quantitatively evaluating the pulsatility of this critical vascular network. Further work is warranted to explore the reproducibility and clinical potential of this approach.

Comparison of placental three-dimensional power Doppler indices and volume in the first and the second trimesters of pregnancy complicated by gestational diabetes mellitus

Objective: To compare the changes of placental three-dimensional power Doppler indices and volume in the first and the second trimesters of pregnancy with gestational diabetes mellitus (GDM). Methods: This was a prospective case-control study of singleton pregnancies with risk factors for GDM. Data on placental vascular indices including vascularization index (VI), flow index (FI), and vascularization flow index (VFI), as well as placental volume were obtained and analyzed during the first and the second trimesters between pregnant women with and without GDM. Results: Of the 155 pregnant women enrolled, 31 developed GDM and 124 did not. VI and VFI were significantly lower in the GDM group during the first and second trimesters (VI: p = .023, and VFI: p = .014 in the first trimester; VI: p = .049, and VFI: p = .031 in the second trimester). However, the placental volume was similar in both the groups during the first trimester, while it was significantly increased in the GDM group during the second trimester (p = .022). There were no significant differences in FI and uterine artery pulsatility index between the two groups. After adjustments in multivariate logistic regression analysis, significant differences were observed in the first trimester VFI (adjusted odds ratio (OR) 0.76, 95% confidence interval (CI) 0.61-0.93), second trimester VFI (adjusted or 0.83, 95%CI 0.71-0.96), and second trimester placental volume (adjusted or 1.03, 95%CI 1.01-1.05). Conclusions: Placental vascular indices can provide an insight into placental vascularization in GDM during early pregnancy. VFI rather than placental volume may be a sensitive sonographic marker in the first trimester of GDM placentas.