Supplementary Material for: Factors Influencing the Accuracy of Fetal Weight Estimation with a Focus on Preterm Birth at the Limit of Viability: A Systematic Literature Review

<b><i>Background:</i></b> Fetal weight estimation (FWE) is an important factor for clinical management decisions, especially in imminent preterm birth at the limit of viability between 23^0/7 and 26^0/7 weeks of gestation. It is crucial to detect and eliminate factors that have a negative impact on the accuracy of FWE. <b><i>Data Sources:</i></b> In this systematic literature review, we investigated 14 factors that may influence the accuracy of FWE, in particular in preterm neonates born at the limit of viability. <b><i>Results:</i></b> We found that gestational age, maternal body mass index, amniotic fluid index and ruptured membranes, presentation of the fetus, location of the placenta and the presence of multiple fetuses do not seem to have an impact on FWE accuracy. The influence of the examiner's grade of experience and that of fetal gender were discussed controversially. Fetal weight, time interval between estimation and delivery and the use of different formulas seem to have an evident effect on FWE accuracy. No results were obtained on the impact of active labor. <b><i>Discussion:</i></b> This review reveals that only few studies investigated factors possibly influencing the accuracy of FWE in preterm neonates at the limit of viability. Further research in this specific age group on potential confounding factors is needed.

<b><i>背景：</i></b> 胎儿体重评估（Fetal Weight Estimation, FWE）是临床管理决策的重要参考因素，尤其针对孕23⁰/₇至26⁰/₇周、处于可存活极限的即将发生早产病例。检测并消除对FWE准确性存在负面影响的因素，具有重要临床意义。<b><i>数据来源：</i></b> 本项系统文献综述共调研了14项可能影响FWE准确性的因素，重点聚焦于极可存活孕周出生的早产新生儿群体。<b><i>结果：</i></b> 研究发现，胎龄、产妇体重指数、羊水指数、胎膜破裂、胎儿先露、胎盘位置以及多胎妊娠，似乎均不会对FWE准确性产生影响。检查者经验等级与胎儿性别的影响目前尚存争议。胎儿体重、评估至分娩的时间间隔以及不同评估公式的使用，似乎对FWE准确性存在显著影响。关于产程活跃期对FWE准确性的影响，本综述未获得相关研究结果。<b><i>讨论：</i></b> 本综述显示，当前针对极可存活孕周早产新生儿群体中可能影响FWE准确性的相关因素研究较为匮乏，仍需针对该特定孕周群体开展潜在混杂因素的后续研究。