Supplementary Material for: Gestational Age-Adjusted Reference Ranges for Fetal Left Ventricle Longitudinal Strain by Automated Cardiac Motion Quantification between 24 and 37 Weeks’ Gestation

<b><i>Introduction:</i></b> The objective of this study was to construct gestational age (GA) based reference values for left ventricle (LV) longitudinal strain in normal fetuses, between 24 and 37 weeks’ gestation, assessing its feasibility and reproducibility with automated cardiac motion quantification software (aCMQ-QLab), which is widely used in postnatal echocardiography. <b><i>Methods:</i></b> This prospective study included healthy gravid women with singleton pregnancies and no evidence of fetal structural cardiovascular disease. Fetal echocardiographies were performed between 24 and 37 GA. 2D four-chamber view clips were recorded and LV longitudinal strain was analyzed offline. Intra- and interobserver reproducibility between 2 independent observers was evaluated by intraclass correlation coefficients (ICC) and Bland-Altman scatterplots. Regression analysis was used to determine GA adjusted reference ranges and construct nomograms. <b><i>Results:</i></b> LV longitudinal strain measurements were feasible in 95.4% of acquisitions. 435 clips were obtained. Intra- and interobserver ICC were 0.998 (95% CI 0.997–0.999) and 0.991 (95% CI 0.984–0.995), respectively. The global longitudinal strain and the middle and apical LV segments showed progressive decline as GA advanced, whereas the basal segments remained stable. <b><i>Conclusions:</i></b> Assessment of LV longitudinal strain by aCMQ-QLab is feasible, reproducible, and within normal ranges. Our results offer more information regarding fetal cardiac function assessment with 2D speckle tracking techniques, aiding in the introduction of this software into research practice, encouraging the realization of more studies, and probably helping in its future use in clinical practice, allowing longitudinal surveillance of strain without intervendor variability and aiding in follow-up of fetal cardiac conditions before and after birth, as it is the most commonly used software postnatally.

**<i>引言：</i>** 本研究旨在构建孕24至37周正常胎儿左心室（left ventricle，LV）纵向应变的孕周（gestational age，GA）参考值，并评估其采用产后超声心动图领域广泛应用的自动化心脏运动定量软件（automated cardiac motion quantification software，aCMQ-QLab）进行检测的可行性与重复性。**<i>方法：</i>** 本前瞻性研究纳入单胎妊娠且无胎儿结构性心血管疾病证据的健康妊娠妇女。于孕24至37周期间完成胎儿超声心动图检查，记录二维四腔心切面视频片段并离线分析左心室纵向应变。由2名独立观察者分别开展评估，通过组内相关系数（intraclass correlation coefficients，ICC）与Bland-Altman散点图评价观察者内及观察者间重复性。采用回归分析确定孕周校正后的参考范围并构建列线图。**<i>结果：</i>** 95.4%的采集操作可成功完成左心室纵向应变测量，共获取435段视频片段。观察者内与观察者间组内相关系数分别为0.998（95%置信区间0.997–0.999）与0.991（95%置信区间0.984–0.995）。随着孕周增加，整体纵向应变及左心室心尖、中段的纵向应变呈进行性下降趋势，而基底段应变保持稳定。**<i>结论：</i>** 采用aCMQ-QLab软件评估左心室纵向应变具备可行性与重复性，且结果处于正常参考范围内。本研究为二维斑点追踪技术在胎儿心功能评估中的应用提供了更多参考信息，有助于推动该软件在科研实践中的应用，鼓励更多相关研究开展，并有望助力其未来应用于临床实践：该软件作为产后最常用的超声定量工具，可实现无仪器间差异的应变纵向监测，辅助出生前后胎儿心脏疾病的随访管理。