[Reference values and growth curves of weight/length, body mass index, and ponderal index of Chinese newborns of different gestational ages].

Objective: To establish the reference values and growth curves of weight/length, body mass index, and ponderal index for Chinese newborns with gestational ages of 24 to 42 weeks, in order to provide a reference for the assessment of body proportionality and nutritional status at birth. Methods: Cross-sectional study design was applied. From June 2015 to November 2018, a total of 24 375 singleton live birth newborns with gestational ages of 24 to 42 weeks from 13 cities including Beijing, Harbin, Xi'an, Shanghai, Nanjing, Wuhan, Guangzhou, Fuzhou, Kunming, Tianjin, Shenyang, Changsha, and Shenzhen were selected, excluding those impacting the establishment of the reference values. The generalized additive model for location, scale, and shape (GAMLSS) was employed to establish percentile (P3, P10, P25, P50, P75, P90, P97) reference values and growth curves of weight/length, body mass index, and ponderal index for male and female newborns with gestational ages of 24 to 42 weeks. The established growth standards in this study were compared with the standards from the 1988 Chinese data, the INTERGROWTH project, and the USA reference values. Results: A total of 24 375 newborns with 12 264 preterm newborns (7 042 males and 5 222 females) and 12 111 full-term newborns (6 155 males and 5 956 females) were included in this study. The percentile reference values and growth curves of weight/length, body mass index, and ponderal index were obtained for male and female newborns with gestational ages of 24 to 42 weeks. Weight/length of males in all gestational ages at P10, P50 and P90 was 0 to 0.2 kg/m higher than that of females, and body mass index of males in all gestational ages at the P10, P50 and P90 was 0.1 to 0.3 kg/m2 higher than that of females. The established growth curves of weight/length and body mass index at the upper percentile and ponderal index at both upper and lower percentiles were greatly different from those of the 1988 Chinese data, which, for example, reported the difference ranges at P90 as -1.09 to 0.40 kg/m for weight/length, -1.19 to 0.92 kg/m2 for body mass index, and -0.64 to 0.81 kg/m3 for ponderal index. The established weight/length curves were generally consistent with the reference values from the INTERGROWTH project with a difference of -0.17 to 0.20 kg/m at P50, while being 0.02 to 0.40 kg/m lower at P90 and 0.13 to 0.41 kg/m higher at P10 than that of the INTERGROWTH reference values at gestational ages of ≤32 weeks. The established body mass index curves differed from that of the USA reference values with a difference of -0.47 to 0.17 kg/m2 at P50, while being 0.53 to 1.10 kg/m2 lower at gestational ages of ≥37 weeks but 0.17 to 0.45 kg/m2 higher at gestational ages of ≤28 weeks than that of the USA reference values at P90. Conclusion: The establishment of the new standardized growth reference values of weight/length, body mass index, and ponderal index for Chinese newborns by different gestational ages are useful for clinical practice and scientific research.