Supplementary Material for: Uterine Artery Pulsatility Index Assessment at 11-13⁺⁶ Weeks' Gestation

<b><i>Introduction:</i></b> First-trimester uterine artery pulsatility index (PI) measurements form part of an algorithm used to assess the risk of developing pre-eclampsia. The objective of this study was to construct a population-specific reference range for both the lower and mean maternal uterine artery PI at 11-13⁺⁶ weeks' gestation and to assess measurement agreement. <b><i>Materials and Methods:</i></b> Reference ranges for mean and lower PI measurements were developed using polynomial regression models following prospective collection of maternal uterine artery PI measurements at 11-13⁺⁶ weeks' gestation. Measurement agreement studies were performed by two experienced operators. <b><i>Results:</i></b> Measurements from 298 women were included in the primary study. Polynomial regression indicated no change over gestational age for the lower PI (mean 1.44). There was an inverse relationship between the average PI and gestational age (mean [0.8960 + (2.9771 × CRL^-1/2)]²). PI measurement agreement was good-strong (intraclass correlation (ICC) 0.50-0.79) between operators, and within-operator agreement was almost perfect (ICC 0.88-0.93). <b><i>Conclusions:</i></b> Reference ranges for both the average and lowest PI of the maternal uterine arteries were derived at 11-13⁺⁶ weeks' gestation. This will provide a basis for development of auditable standards for first-trimester uterine artery Doppler measurements. The PI measurements are reproducible and reliable.<b><i>引言：</i></b> 孕早期子宫动脉搏动指数（PI）测量是子痫前期发病风险评估算法的组成部分。本研究旨在构建孕11~13⁺⁶周时孕妇子宫动脉最低搏动指数与平均搏动指数的人群特异性参考范围，并评估测量一致性。<b><i>材料与方法：</i></b> 本研究通过前瞻性收集孕11~13⁺⁶周孕妇的子宫动脉PI测量数据，采用多项式回归模型构建平均与最低PI的参考范围。由两名经验丰富的检测操作者开展测量一致性研究。<b><i>结果：</i></b> 本研究纳入298名女性的测量数据。多项式回归分析显示，最低PI随孕周无明显变化，均值为1.44。平均PI与孕周呈负相关，计算公式为均值[0.8960 + (2.9771 × 头臀长（CRL）^-1/2)]²。操作者间的PI测量一致性为良好至较强水平（组内相关系数（ICC）0.50~0.79），操作者内部测量一致性近乎完美（ICC 0.88~0.93）。<b><i>结论：</i></b> 本研究构建了孕11~13⁺⁶周孕妇子宫动脉平均搏动指数与最低搏动指数的参考范围。该参考范围可为孕早期子宫动脉多普勒测量的可审核标准制定提供依据。PI测量具有良好的可重复性与可靠性。