Hediger M L, Overpeck M D, McGlynn A, Kuczmarski R J, Maurer K R, Davis W W
Division of Epidemiology, Statistics and Prevention Research, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-7510, USA.
Pediatrics. 1999 Sep;104(3):e33. doi: 10.1542/peds.104.3.e33.
To compare young children 3 to 6 years of age who were born small-for-gestational age (SGA; <10th percentile for gestational age) or large-for-gestational age (LGA; >/=90th percentile) with those who were born appropriate-for-gestational age (10th-89th percentile) to determine whether there are differences in growth and fatness in early childhood associated with birth weight status.
National sample of 3192 US-born non-Hispanic white, non-Hispanic black, and Mexican-American children 3 to 6 years of age (36-83 months) examined in the third National Health and Nutrition Examination Survey and for whom birth certificates were obtained. On the birth certificates, length of gestation from the mother's last menstrual period was examined for completeness, validity, and whether the pattern of missing (n = 141) and invalid data (n = 147) on gestation was random. Gestation was considered invalid when >44 weeks, or when at gestations of </=35 weeks, birth weight was inconsistent with gestation. To reclaim cases with missing or invalid data on gestation for analysis, a multiple imputation (MI) procedure was used. MI procedures are recommended when, as in this case, a critical covariate (length of gestation) is not missing at random, and complete-subject analysis may be biased. Using the results of the MI procedure, children were categorized, and growth outcome was assessed by birth weight-for-gestational age status. The growth outcomes considered in these analyses were body weight (kg), height (cm), head circumference (cm), mid-upper arm circumference (MUAC; cm), and triceps and subscapular skinfold thicknesses (mm). The anthropometric outcomes first were transformed to approximate normal distributions and converted into z scores (standard deviation units [SDU]) to scale the data for comparison across ages. Outcomes at each age then were estimated using regression procedures. SUDAAN software that adjusts variance estimates to account for the sample design was used in analysis for prevalence estimates and to calculate regression coefficients (in SDU).
Over these ages, children born SGA remained significantly shorter and weighed less (-0.70 to -0.60 SDU). Children born LGA remained taller and weighed more (0.40-0.60 SDU). For weight and height among LGA children, there was a divergence from the mean with age compared with those born appropriate-for-gestational age (10th-89th percentile). Head circumference and MUAC followed these same patterns. The coefficients for MUAC show values for SGA children fairly consistently at about -0.50 SDU and children born LGA show increasing MUAC from +0.40 to +0.50 SDU from 36 to 83 months of age. As with weight, there is a trend toward increased MUAC coefficients with age. Measures of fatness (triceps and subscapular skinfolds), which are more prone to environmental influences, showed less association with birth weight-for-gestational age status. Only a single age group, the oldest (6 years of age) group showed a significant deficit in fatness for children born SGA. For children born LGA, there was an increase in fatness at both the triceps and subscapular sites after 3 years of age.
These findings on a national sample of US-born non-Hispanic white, non-Hispanic black, and Mexican-American children show that children born SGA remain significantly shorter and lighter throughout early childhood and do not seem to catch up from 36 to 83 months of age. LGA infants remain longer and heavier through 83 months of age, but unlike children born SGA, children born LGA may be prone to an increasing accumulation of fat in early childhood. Thus, early childhood may be a particularly sensitive period in which there is increase in variation in levels of fatness associated with size at birth. These findings have implications for the evaluation of the growth of young children. The results indicate that intrauterine growth is associated with size in early childhood. (ABSTR
比较出生时小于胎龄（SGA；胎龄小于第10百分位数）或大于胎龄（LGA；胎龄大于或等于第90百分位数）的3至6岁幼儿与出生时适于胎龄（第10 - 89百分位数）的幼儿，以确定幼儿期生长和肥胖情况与出生体重状况是否存在差异。
对3192名在美国出生的3至6岁（36 - 83个月）非西班牙裔白人、非西班牙裔黑人及墨西哥裔美国儿童进行全国抽样调查，这些儿童参加了第三次全国健康与营养检查调查，并获取了他们的出生证明。在出生证明上，检查母亲末次月经后的孕周长度是否完整、有效，以及孕周缺失（n = 141）和无效数据（n = 147）的模式是否随机。当孕周大于44周，或孕周小于或等于35周且出生体重与孕周不符时，孕周被视为无效。为了回收孕周数据缺失或无效的病例进行分析，采用了多重填补（MI）程序。当关键协变量（孕周长度）并非随机缺失且完整对象分析可能存在偏差时，如本案例，推荐使用MI程序。利用MI程序的结果对儿童进行分类，并根据出生体重与胎龄状况评估生长结局。这些分析中考虑的生长结局包括体重（kg）、身高（cm）、头围（cm）、上臂中部周长（MUAC；cm）以及肱三头肌和肩胛下皮褶厚度（mm）。首先将人体测量学结局转换为近似正态分布，并转换为z分数（标准差单位[SDU]），以便对不同年龄的数据进行比较。然后使用回归程序估计每个年龄的结局。分析患病率估计值并计算回归系数（以SDU为单位）时，使用了能调整方差估计以考虑样本设计的SUDAAN软件。
在这些年龄段，出生时小于胎龄的儿童仍然明显更矮、更轻（-0.70至-0.60 SDU）。出生时大于胎龄的儿童仍然更高、更重（0.40 - 0.60 SDU）。与出生时适于胎龄（第10 - 89百分位数）的儿童相比，大于胎龄儿童的体重和身高随年龄增长与均值出现偏差。头围和MUAC也呈现相同模式。MUAC的系数显示，小于胎龄儿童的值相当一致地约为-0.50 SDU，而出生时大于胎龄的儿童在36至83个月龄时，MUAC从+0.40增加到+0.50 SDU。与体重一样，MUAC系数有随年龄增加的趋势。更易受环境影响的肥胖指标（肱三头肌和肩胛下皮褶）与出生体重与胎龄状况的关联较小。只有最年长的（6岁）年龄组显示，出生时小于胎龄的儿童存在明显的肥胖不足。对于出生时大于胎龄的儿童，3岁后肱三头肌和肩胛下部位的肥胖均有所增加。
这些对在美国出生的非西班牙裔白人、非西班牙裔黑人及墨西哥裔美国儿童全国样本的研究结果表明，出生时小于胎龄的儿童在幼儿期始终明显更矮、更轻，且在36至83个月龄时似乎没有追赶上来。大于胎龄的婴儿在83个月龄前一直更高、更重，但与出生时小于胎龄的儿童不同，出生时大于胎龄的儿童在幼儿期可能更容易出现脂肪堆积增加的情况。因此，幼儿期可能是一个特别敏感的时期，此时与出生时大小相关的肥胖水平差异会增加。这些发现对幼儿生长评估具有重要意义。结果表明，宫内生长与幼儿期大小相关。（摘要）
