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Why Adding Placental Volume to FGR Screening is Crucial

•Posted inObstetrics and Gynaecology

Fetal Growth Restriction (FGR) remains a leading cause of perinatal morbidity and mortality worldwide. New findings from the First-trimester Placental Ultrasound (FirstPLUS) study demonstrate a significant enhancement in FGR prediction models by incorporating first-trimester placental volume (FTPV). Consequently, clinicians now have a more powerful tool for early-stage risk stratification, which is especially vital for timely intervention.

The Study’s Methodology

The FirstPLUS study was a longitudinal, observational cohort conducted in London, UK. Researchers utilized data from 3500 pregnancies, identifying FGR in 7.1% (250 cases) of the cohort. Furthermore, participants underwent routine first-trimester ultrasound screening between 11+2 and 14+1 weeks’ gestation. The study integrated three-dimensional placental sonography and used the automated OxNNet toolkit to accurately calculate the FTPV. Moreover, the final predictive models used multivariable logistic regression, combining FTPV with established metrics like maternal factors, serum PAPP-A, mean arterial blood pressure, and uterine artery pulsatility index. This rigorous approach allowed for a clear assessment of FTPV’s distinct contribution to FGR prediction.

Key Findings: FTPV as an Independent Predictor

Low First-trimester placental volume proved an independent risk factor for FGR. Specifically, researchers reported an odds ratio of 1.736 for FGR per unit decrease in FTPV Z-score. Incorporating FTPV into the existing maternal and biomarker-based models significantly improved the overall predictive capability. For all cases of FGR, the Area Under the Curve (AUC) for the predictive model increased from 0.78 to 0.79 (P=0.005). This statistical improvement confirms the clinical utility of the new metric. Therefore, the data suggests that placental size in the early first trimester directly correlates with placental function and subsequent fetal growth.

Impact on Normotensive FGR

The study also performed a subgroup analysis, distinguishing between normotensive and hypertensive cases. Importantly, the addition of FTPV enhanced the prediction for normotensive FGR. In this specific subgroup, the model’s AUC increased from 0.77 to 0.78 (P=0.01). However, a statistically significant difference was not observed for preterm FGR prediction, which the authors suggest may be due to a lack of power in that small subgroup. Nevertheless, low FTPV Z-score demonstrated a statistically significant effect size for FGR prediction in both normotensive and hypertensive groups.

Clinical Significance for Indian Practice

Using first-trimester screening to predict FGR is highly relevant in India. A smaller early placental volume has already been strongly associated with both FGR and preeclampsia. Furthermore, Indian studies have explored biophysical models, including placental length and volume, in combination with uterine artery PI, demonstrating a 60% detection rate for early-onset FGR in the first trimester. Therefore, the FirstPLUS findings validate and strengthen the clinical argument for integrating 3D placental volume assessment, like FTPV, into existing Indian first-trimester screening protocols. Consequently, this improved model can help clinicians triage high-risk patients earlier, allowing for timely initiation of monitoring and prophylactic measures like low-dose aspirin.

Frequently Asked Questions

Q1: What is the main finding of the FirstPLUS study?

The study found that first-trimester placental volume (FTPV) Z-score is an independent predictor of FGR. Integrating this volume into existing screening models significantly enhanced the discriminative ability for predicting all cases of FGR, especially in the normotensive subgroup.

Q2: How much did FTPV improve the predictive model for all FGR cases?

The addition of FTPV to models based on maternal factors and first-trimester biomarkers increased the Area Under the Receiver-Operating-Characteristics Curve (AUC) for predicting all FGR cases from 0.78 to 0.79 (P=0.005).

Q3: How is this relevant to clinical practice in India?

FGR prediction using first-trimester screening is a focus in India. The FirstPLUS findings support the existing local research that uses placental volume and other biophysical markers to identify patients at high risk of early-onset FGR, thus enabling earlier patient triage and management.

References

  1. Mathewlynn S et al. First-trimester Placental Ultrasound (FirstPLUS) study: prediction of fetal growth restriction using OxNNet-derived first-trimester placental volume. Ultrasound Obstet Gynecol. 2025 Dec 06. doi: 10.1002/uog.70146. PMID: 41351882.
  2. Díaz-Gómez M et al. First trimester 3D ultrasound placental volume for predicting preeclampsia and/or intrauterine growth restriction. J Matern Fetal Neonatal Med. 2018 Dec;31(23):3152-3158. doi: 10.1080/14767058.2017.1373570. Epub 2017 Sep 25.
  3. Kumari M et al. Placental biophysical model for prediction of early onset fetal growth restriction in first and second trimester of pregnancy: A prospective cohort study. Placenta. 2024 Sep 2:154:153-159. doi: 10.1016/j.placenta.2024.07.003. Epub 2024 Jul 4.