[Reference values and growth curves of length for weight and head circumference for weight among Chinese newborns].

Objective: To establish the reference values and growth curves of length for weight and head circumference for weight among Chinese newborns in order to provide a reference for the assessment of body proportionality at birth. Methods: A cross-sectional design was applied. A total of 24 375 singleton live birth newborns with gestational ages at birth of 24+0 to 42+6 weeks were recruited from June 2015 to November 2018 from 13 cities including Beijing, Harbin, Xi'an, Shanghai, Nanjing, Wuhan, Guangzhou, Fuzhou, Kunming, Tianjin, Shenyang, Changsha, and Shenzhen, excluding those with maternal or newborn conditions that may impact the establishment of the reference values. The generalized additive model for location, scale, and shape was employed to establish reference values in terms of percentile and growth curves of length for weight and head circumference for weight for male and female newborns. The random forest machine learning method was employed to analyze the importance of variables between the established reference values in this study and the previous published weight/length, body mass index (BMI), ponderal index (PI), weight/head circumference, length/head circumference in the assessment of symmetrical and asymmetrical small for gestational age (SGA) newborns. Results: A total of 24 375 newborns with 13 197 male infants (preterm birth 7 042 infants and term birth 6 155 infants) and 11 178 female infants (preterm birth 5 222 infants and term birth 5 956 infants) were included in this study. The reference values in terms of percentile (P3, P10, P25, P50, P75, P90, P97) and growth curves of length for weight and head circumference for weight were obtained for male and female newborns with gestational ages of 24+0 to 42+6 weeks. The median birth lengths corresponding to the birth weights of 1 500, 2 500, 3 000, and 4 000 g were 40.4, 47.0, 49.3 and 52.1 cm for males and 40.4, 47.0, 49.2, and 51.8 cm for females, respectively; the median birth head circumferences were 28.4, 32.0, 33.2 and 35.2 cm for males and 28.4, 32.0, 33.1, and 35.1 cm for females, respectively. The differences of length for weight between males and females were minimum, with the difference range of -0.3 to 0.3 cm at P50; the differences of head circumference for weight between males and females were minimum, with the difference range of 0 to 0.2 cm at P50. Based on the match between birth length and birth weight for classifying symmetrical and asymmetrical SGA, length for weight and PI contributed the most, accounting for 0.32 and 0.25, respectively; based on the match between birth head circumference and birth weight, head circumference for weight and weight/head circumference contributed the most, accounting for 0.55 and 0.12, respectively; based on the match between birth length or head circumference with birth weight, head circumference for weight and length for weight contributed the most, accounting for 0.26 and 0.21, respectively. Conclusion: The establishment of the new standardized growth reference values and growth curves of length for weight and head circumference for weight among Chinese newborns are useful for clinical practice and scientific research.目的： 制定中国新生儿体重的身长和体重的头围参照标准及生长曲线，为新生儿出生时身体比例评价提供参考依据。 方法： 横断面研究，于2015年6月至2018年11月在北京、哈尔滨、西安、上海、南京、武汉、广州、福州、昆明、天津、沈阳、长沙、深圳13个城市调查出生胎龄24+0~42+6周单胎活产新生儿24 375名，排除影响参照标准建立的母亲及新生儿因素。采用基于位置、尺度和形状的广义可加模型构建男、女新生儿体重的身长和体重的头围的百分位数参照值及生长曲线。采用随机森林机器学习方法将研制的参照标准与已报道的体重身长比、体质指数、重量指数、体重头围比、身长头围比5个身体比例指标在小于胎龄儿匀称型和非匀称型判别中进行变量重要性分析。 结果： 24 375名新生儿中男13 197名（早产7 042名、足月6 155名）、女11 178名（早产5 222名、足月5 956名）。制定出生胎龄24+0~42+6周男、女新生儿体重的身长和体重的头围的百分位数（P3、P10、P25、P50、P75、P90、P97）参照值及生长曲线。在出生体重1 500、2 500、3 000、4 000 g时男性对应的出生身长中位数分别为40.4、47.0、49.3、52.1 cm，女性分别为40.4、47.0、49.2、51.8 cm；男性对应的出生头围中位数分别为28.4、32.0、33.2、35.2 cm，女性分别为28.4、32.0、33.1、35.1 cm。男、女新生儿体重的身长和体重的头围差异均较小，在P50上差值范围分别为-0.3~0.3和0~0.2 cm。以出生身长是否与出生体重相匹配进行小于胎龄儿匀称型和非匀称型临床分型时，体重的身长和重量指数贡献较大，分别占0.32和0.25；以出生头围是否与出生体重相匹配进行临床分型时，体重的头围和体重头围比贡献较大，分别占0.55和0.12；以出生身长或头围是否与出生体重相匹配进行临床分型时，体重的头围和体重的身长贡献较大，分别占0.26和0.21。 结论： 建立中国男、女新生儿体重的身长和体重的头围的标准化参照值及生长曲线，可供临床及科研相关工作参照使用。.