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Crucial New Charts for First-Trimester Placental Blood Flow

•Posted inObstetrics and Gynaecology

Placental function is central to a healthy pregnancy. Researchers recently established new reference charts for first-trimester placental three-dimensional single-vessel fractional moving blood volume (Placental svFMBV). This vital work uses data from a large cohort of healthy pregnancies. Therefore, these charts provide a critical new baseline for assessing uteroplacental vasculature and predicting adverse outcomes.

Why Quantify Placental svFMBV?

Inadequate placental vascularity during early gestation is strongly linked to severe complications. Specifically, it can lead to pre-eclampsia (PE) and fetal growth restriction (FGR). Standard power Doppler indices have proven inconsistent for quantitative, inter-patient comparison. Consequently, physicians need a standardized, reliable metric.

Furthermore, previous research on the original 3D fractional moving blood volume (3D-FMBV) technique showed significantly decreased vascularity in pregnancies destined to develop pre-eclampsia. This novel, fully-automated 3D-svFMBV method improves on the prior technique. It offers more biologically plausible perfusion estimates and shows improved prediction accuracy for pre-eclampsia. Therefore, having robust reference charts for Placental svFMBV is key for early risk stratification.

Developing Reference Charts for Placental svFMBV

The study used data from the First-trimester Placental Ultrasound (FirstPLUS) cohort, a large-scale observational study. Investigators conducted 3D ultrasound assessments with power Doppler on over 2,500 healthy singleton pregnancies. The novel OxNNet toolkit then provided automated placental segmentation and 3D-svFMBV calculation. This automation enhances reproducibility.

Next, the researchers performed extensive quality control to ensure image completeness and segmentation accuracy. They used sophisticated statistical methods, including quantile regression and the Lambda-Mu-Sigma (LMS) modeling approach, to construct the reference charts. Notably, the LMS method provided the best fit for modeling the positively skewed data distribution. Ultimately, the resulting centile charts established the normal range for placental blood flow at five specific locations within the uteroplacental vasculature. Physicians can now confidently use this new data to explore placental function.

Frequently Asked Questions

Q1: What is Placental svFMBV?

Placental svFMBV, or single-vessel fractional moving blood volume, is a standardized, quantitative measure of placental tissue perfusion. It uses 3D power Doppler ultrasound, calibrated to a single large blood vessel, to correct for tissue attenuation and machine setting variability.

Q2: How does the OxNNet toolkit improve the measurement?

The OxNNet toolkit uses a fully convolutional neural network for automated placental segmentation and 3D-svFMBV calculation. This automation standardizes the measurement process, thereby reducing operator variability and improving the accuracy and robustness of the placental perfusion estimate.

Q3: What is the clinical significance of these reference charts?

These new reference charts establish the normal range for first-trimester Placental svFMBV in healthy pregnancies. Consequently, clinicians can identify abnormally low blood flow values, which serve as an early biomarker for severe placental disorders such as pre-eclampsia and fetal growth restriction.

References

  1. Mathewlynn S et al. Reference charts for first-trimester placental three-dimensional fractional moving blood volume derived using OxNNet. Ultrasound Obstet Gynecol. 2026 Jan 07. doi: 10.1002/uog.70161. PMID: 41499517.
  2. Szafranska E et al. 3D Single Vessel Fractional Moving Blood Volume (3D-svFMBV): Fully Automated Tissue Perfusion Estimation Using Ultrasound. IEEE Trans Med Imaging. 2024 Jul;43(7):2707-2717. doi: 10.1109/TMI.2024.3377721. PMID: 38478454.
  3. Collins SL et al. 3D fractional moving blood volume (3D-FMBV) demonstrates decreased first trimester placental vascularity in pre-eclampsia but not the term, small for gestation age baby. PLoS One. 2017 Jun 1;12(6):e0178693. doi: 10.1371/journal.pone.0178693. PMID: 28570535.
  4. Mathewlynn S et al. Reference charts for first-trimester placental volume derived using OxNNet. Ultrasound Obstet Gynecol. 2025 Sep;66(3):337-346. doi: 10.1002/uog.29300. PMID: 40746163.