Supplementary Material for: Mortality Risk in US NICU Infants by Birth Size Classifications Comparing Three Growth Curves

Introduction: Three widely referenced growth curves classify infant birth anthropometric measurements as small (SGA), appropriate (AGA), or large (LGA) for gestational age (GA) differently. We assessed how these differences in assignment affect the identification and prediction of neonatal intensive care unit (NICU) mortality risk in US preterm infants. Methods: Birth data of infants admitted to NICUs from the Pediatrix Clinical Data Warehouse (2013-2018) were analyzed. Birth weight, length, and head circumference of 46,724 singleton infants (24-32 weeks’ GA) were classified as SGA, AGA, or LGA using the Olsen, Fenton, and INTERGROWTH–21st curves. NICU mortality risk based on birth size classification was analyzed using unadjusted and adjusted logistic regression stratified by GA. Results: Odds of mortality were increased with SGA classification at all GAs, size measurements and curve sets, compared with AGA infants. LGA classification for weight was associated with lower mortality risk at 24 weeks GA and higher risk at 30 weeks GA. Odds of mortality did not differ significantly across curve sets. Classification of size at birth alone had relatively low predictive ability to identify mortality risk, with unadjusted AUCs near 0.5 for all analyses. Discussion/Conclusion: There were no significant differences across curve sets in predicting mortality. Classification of size at birth is a relatively imprecise method to identify infants at risk for NICU mortality.

引言：目前有3种被广泛引用的生长曲线，针对胎龄（gestational age, GA）对新生儿出生人体测量学指标进行分类时，对小于胎龄儿（small for gestational age, SGA）、适于胎龄儿（appropriate for gestational age, AGA）及大于胎龄儿（large for gestational age, LGA）的判定标准存在差异。本研究旨在评估这类分类差异对美国早产新生儿重症监护病房（neonatal intensive care unit, NICU）死亡风险的识别与预测所产生的影响。
方法：本研究分析了2013至2018年来自Pediatrix临床数据仓库的新生儿重症监护病房收治患儿的出生数据。研究纳入46724名单胎婴儿（胎龄24~32周），分别采用Olsen、Fenton及INTERGROWTH-21st生长曲线，对其出生体重、身长及头围进行小于胎龄儿、适于胎龄儿或大于胎龄儿分类。按胎龄分层后，采用未校正与校正后的logistic回归模型，分析基于出生体尺寸分类的新生儿重症监护病房死亡风险。
结果：与适于胎龄儿相比，所有胎龄组别、体尺寸测量指标及生长曲线分组下，小于胎龄儿的死亡比值比均显著升高。体重分类为大于胎龄儿的婴儿，在胎龄24周时死亡风险更低，而在胎龄30周时死亡风险更高。不同生长曲线分组间的死亡比值比无显著差异。仅依靠出生体尺寸分类识别死亡风险的预测能力相对有限，所有分析的未校正受试者工作特征曲线下面积（AUC）均接近0.5。
讨论与结论：不同生长曲线分组在预测新生儿重症监护病房死亡风险方面无显著差异。仅通过出生体尺寸分类来识别存在新生儿重症监护病房死亡风险的患儿，是一种相对不够精准的方法。