Abstract: Background　Two years after birth is a critical period for small for gestational age（SGA）infants to complete catch-up growth.Their growth is special compared with appropriate for gestational age（AGA）.However，there are no guidelines for early follow-up for SGA infants，and their early growth characteristics need further study.Objective　To investigate the physical growth of SGA infants in 24 months after birth.Methods　A prospective cohort design was used.SGA infants who were born from March 2016 to March 2017 and received regular physical examination in Department of Child Healthcare，Xiamen Maternal and Child Healthcare Hospital within 2 years after birth，as well as full-term AGA infants born during the same period were selected.According to the Chinese neonatal birth weight curve for different gestational age in 2015，combined with gestational age and birth weight，they were divided into full-term SGA group（n=147），preterm SGA group（n=42） and full-term AGA group（n=164）.The weight，length and head circumference were measured at birth，3 months（±7 d），6 months（±7 d），12 months（±14 d），18 months（±14 d）and 24 months（±14 d），and growth level and growth rate were analyzed after z-score conversion.Results　The results of repeated measures ANOVA showed that there were interactions between groups and time on WAZ，LAZ，BMIZ and HCZ，and the main effects were significant（P<0.05）.The simple effect analysis showed that the WAZ，LAZ，BMIZ and HAZ at each time point differed significantly across the groups（P<0.05）.WAZ，LAZ，and BMIZ at different ages were significant across the groups（P<0.05）.The WAZ of the full-term AGA group was greater than that of other two groups either at 3，6，12，18 or 24 months（P<0.05），so were the LAZ and HCZ of the full-term AGA group（P<0.05）.In terms of BMIZ，full-term AGA group had greater BMIZ at 3，6，12，18，and 24 months than full-term SGA group（P<0.05）.Full-term AGA group showed greater BMIZ at 3 and 6 months than preterm SGA group（P<0.05）.The differences between the 3 groups were significant in ?WAZ at 0-3 months，3-6 months and 6-12 months（P<0.05）.To be specific，the ?WAZ at 0-3 months in full-term AGA group was less than that of other two groups（P<0.05）.The ?WAZ at 3-6 months in the full-term SGA group was higher than that of full-term AGA group（P<0.05）.The differences between the groups were significant in ?LAZ at 3-6 months and 6-12 months（P<0.05）.Specifically，the full-term SGA group showed higher ?LAZ at 3-6 months and 6-12 months than full-term AGA group（P<0.05）.The ?BMIZ at 0-3 months and 6-12 months differed significantly across the groups（P<0.05）.More concretely，full-term AGA group showed less ?BMIZ at 0-3 and 6-12 months than other two groups（P<0.05）.The ?BMIZ at 0-3 months in the preterm SGA group was higher than that in the full-term SGA group（P<0.05）.The ?HCZ at 3-6 months varied significantly across the groups（P<0.05）.The ?HCZ at 0-3 months in full-term AGA group was lower than that of other two groups（P<0.05）.The weight catch-up rates among 3 groups at 3，6，12，18，and 24 months showed significant differences（P<0.05）.In particular，the weight catch-up rates of the full-term and preterm SGA groups were higher at 3，6，12，18 and 24 months（P<0.017）.The differences in length catch-up rates at 6，12，18 and 24 months between the three groups were significant（P<0.05）.In particular，the length catch-up rates of the full-term and preterm SGA groups at 12，18 and 24 months were higher（P<0.017）.Conclusion　The weight and length of SGA infants increase rapidly in the first year of life.Weight catch-up growth is dominant at the age of 0-3 months.The starting point of length catch-up growth is later than that of weight catch-up growth.The head circumference catch-up growth is mainly in the 6 months after birth.In the early stages，the BMI of preterm SGA infants increases more rapidly.

Key words: Child development, Infant development, Small for gestational age, Appropriate for gestational age, Physical growth, Catch-up growth, Preterm

摘要： 背景　出生后2年是小于胎龄儿（SGA）完成追赶生长的关键时期，其生长与适于胎龄儿（AGA）相比具有特殊性，但目前尚缺乏对于早期SGA随访的指南，对于早期SGA生长特点还需进一步研究。目的　探讨SGA出生后2年内的体格生长规律。方法　采用前瞻性队列研究方法，选取出生于2016年3月—2017年3月且出生后2年内定期在厦门市妇幼保健院儿童保健科体检的SGA，以及同期出生的足月AGA作为研究对象，根据2015年中国不同胎龄新生儿出生体质量曲线，结合胎龄和出生体质量分为足月SGA组（n=147）、早产SGA组（n=42）、足月AGA组（n=164），分别在出生时、3月龄（±7 d）、6月龄（±7 d）、12月龄（±14 d）、18月龄（±14 d）、24月龄（±14 d）测量其体质量、身长、头围，经Z值转换后分析其生长水平及生长速度。结果　重复测量方差分析结果显示，组间、时间对年龄别体质量Z值（WAZ）、年龄别身长Z值（LAZ）、年龄别体质指数（BMI）Z值（BMIZ）、年龄别头围Z值（HCZ）存在交互作用，且主效应显著（P<0.05）；简单效应分析显示，3组间WAZ、LAZ、BMIZ、HCZ比较，差异均有统计学意义（P<0.05）；3组各时间点WAZ、LAZ、BMIZ比较，差异均有统计学意义（P<0.05）。足月SGA组和早产SGA组3月龄、6月龄、12月龄、18月龄、24月龄WAZ、LAZ、HCZ小于足月AGA组，足月SGA组3月龄、6月龄、12月龄、18月龄、24月龄BMIZ小于足月AGA组，早产SGA组3月龄、6月龄BMIZ小于足月AGA组（P<0.05）。3组间0~3月龄、>3~6月龄、>6~12月龄?WAZ，>3~6月龄、>6~12月龄?LAZ，0~3月龄、>6~12月龄?BMIZ，>3~6月龄?HCZ比较，差异均有统计学意义（P<0.05）。足月SGA组和早产SGA组0~3月龄?WAZ高于足月AGA组，足月SGA组>3~6月龄?WAZ高于足月AGA组，足月SGA组>3~6月龄、>6~12月龄?LAZ高于足月AGA组，足月SGA组和早产SGA组0~3月龄、>6~12月龄?BMIZ高于足月AGA组，早产SGA组0~3月龄?BMIZ高于足月SGA组，足月SGA组和早产SGA组0~3月龄?HCZ高于足月AGA组（P<0.05）。3组间3月龄、6月龄、12月龄、18月龄、24月龄体质量追赶生长率比较，差异均有统计学意义（P<0.05）；其中，足月SGA组和早产SGA组3月龄、6月龄、12月龄、18月龄、24月龄体质量追赶生长率大于足月AGA组（P<0.017）。3组间6月龄、12月龄、18月龄、24月龄身长量追赶生长率比较，差异均有统计学意义（P<0.05）；其中，足月SGA组和早产SGA组12月龄、18月龄、24月龄身长追赶生长率大于足月AGA组（P<0.017）。结论　出生后1年SGA体质量、身长加速生长。0~3月龄以体质量追赶为主，身长发生追赶时间落后于体质量，头围追赶主要在出生后6月龄内。而早产SGA的BMI在早期增长更加快速。

关键词: 儿童发育, 婴儿发育, 小于胎龄儿, 适于胎龄儿, 体格生长, 追赶生长, 早产