INCIDENCE OF SMALL FOR GESTATIONAL AGE NEONATES, ACCORDING TO THE FENTON AND INTERGROWTH-21ST CURVES IN A LEVEL II MATERNITY

ABSTRACT Objective: To compare the incidence of small for gestational age infants among late preterm and term newborns, using the Fenton and Intergrowth-21st curves. Methods: Observational and retrospective study with newborns in a level II maternity. The study was approved by the Institution’s Ethics Committee. Live births from July 2007 to February 2009 with a gestational age from 34 to 41 weeks and seven days were included. Neonates with incomplete data were excluded. Appropriate weight for gestational age was assessed by the Fenton and Intergrowth-21st intrauterine growth curves, considering birth weight <10th percentile as small for gestational age. The degree of agreement between the two curves was assessed by the Kappa coefficient. Numerical variables were compared using the Student t-test or the Mann-Whitney. Categorical variables were compared using the chi-square test. Statistical analyzes were performed using SPSS17® software, considering significant, p<0.05. Results: We included 2849 newborns with a birthweight of 3210±483 g, gestational age of 38.8±1.4 weeks; 51.1% male. The incidence of small for gestational age in the full sample was 13.0 vs. 8.7% (p<0.001, Kappa=0.667) by the Fenton and Intergrowth-21st curves, respectively. Among late preterm, the incidence of small neonates was 11.3 vs. 10.9% (p<0.001; Kappa=0.793) and among full-term infants it was 13.1% vs. 8.5% (p<0.001; Kappa=0.656), respectively for the Fenton and Intergrowth-21st curves. Conclusions: The incidence of small for gestational age newborns was significantly higher using the Fenton curve, with greater agreement between the Fenton and Intergrowth-21st curves among late preterm, compared to full term neonates.

摘要
研究目的：采用Fenton生长曲线（Fenton curve）与Intergrowth-21st生长曲线（Intergrowth-21st curve），比较晚早产与足月新生儿的小于胎龄儿（small for gestational age, SGA）发生率。
研究方法：本研究为一项针对二级助产机构新生儿的观察性回顾性研究，已通过机构伦理委员会审查。纳入2007年7月至2009年2月期间分娩的活产新生儿，胎龄范围为34周至41周+7天，排除临床资料不完整的新生儿。采用两种生长曲线评估新生儿体重是否适于胎龄，将出生体重低于同胎龄第10百分位数定义为小于胎龄儿。采用Kappa系数（Kappa coefficient）评估两种曲线的一致性；数值变量比较采用Student t检验（Student t-test）或Mann-Whitney检验（Mann-Whitney test）；分类变量比较采用卡方检验（chi-square test）。所有统计分析均使用SPSS17®软件完成，以p<0.05为差异具有统计学意义。
研究结果：本研究共纳入2849例新生儿，出生体重为3210±483g，胎龄为38.8±1.4周，男性占比51.1%。基于Fenton曲线与Intergrowth-21st曲线评估，全样本的小于胎龄儿发生率分别为13.0%与8.7%（p<0.001，Kappa=0.667）。在晚早产新生儿中，两种曲线对应的小于胎龄儿发生率分别为11.3%与10.9%（p<0.001；Kappa=0.793）；在足月新生儿中，该数值分别为13.1%与8.5%（p<0.001；Kappa=0.656）。
研究结论：相较于Intergrowth-21st曲线，采用Fenton曲线评估得到的小于胎龄儿发生率显著更高；且相较于足月新生儿，晚早产新生儿的两种曲线评估结果一致性更佳。