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Updated: Jan 14, 2026
14:19
Fetal Echocardiography and Pulsed-wave Doppler Ultrasound in a Rabbit Model of Intrauterine Growth Restriction
Published on: June 29, 2013
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Factors affecting the umbilical artery Doppler reference values in the second and third trimesters
Sophia Rahimi1,2, John C Kingdom1,3, Arietta Vayenas2
1Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
Summary
Methodological factors, particularly estimated fetal weight (EFW) centile cut-offs, significantly impact umbilical artery pulsatility index (UA-PI) reference charts, contributing to observed heterogeneity in clinical interpretations.
Area of Science:
- Perinatal Medicine
- Fetal Physiology
- Medical Statistics
Background:
- Umbilical artery pulsatility index (UA-PI) is a key indicator of fetal well-being.
- Published UA-PI reference charts exhibit considerable heterogeneity, complicating accurate clinical interpretation.
- Methodological variations in chart construction are suspected contributors to this heterogeneity.
Purpose of the Study:
- To investigate the influence of specific methodological factors on the variability of published UA-PI reference charts.
- To identify which factors, such as cohort characteristics and statistical modeling, contribute most to chart heterogeneity.
Main Methods:
- Analysis of a large dataset (25,069 UA-PI measurements from 12,394 pregnancies) from uncomplicated singleton pregnancies.
- Exploration of the impact of cohort characteristics: parity and estimated fetal weight (EFW) centile cut-offs.
- Assessment of the effect of different statistical modeling approaches for constructing UA-PI centile reference charts.
Main Results:
- The inclusion cut-off for EFW centiles significantly affected UA-PI centile values; higher cut-offs led to increased detection of elevated UA-PI.
- Charts using EFW >25th or 50th centiles identified more small-for-gestational-age fetuses with UA-PI >95th centile compared to charts using EFW >10th centile.
- Parity and statistical modeling methods had minimal impact on the resulting UA-PI reference charts.
Conclusions:
- The distribution of EFW centiles within the population used to create UA-PI reference charts is a major driver of heterogeneity.
- Clinical interpretation of UA-PI may vary significantly depending on the reference chart's construction methodology, particularly its EFW inclusion criteria.
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