The purpose of present study was to explore the trajectories of growth of preterm and term infants of low, high, and appropriate birth weight. A total of 2465 infants were recruited from 2005 to 2007. Infants' length and weight were measured at 12 points: birth, 42 days, and monthly from 3 to 12 months. The catch-up growth of preterm infants, measured by weight or length of chronological age, occurred from 10th or 12th month of their lives. After adjusted gestational age, preterm infants' weight and length were caught-up from the adjusted birthday, overweight/over-length even occurred from 10th/11th month. For low birth weight term infants, catch-up growth was not found when using single weight or length. The ponderal index catch-up growth occurred earlier than measured by single weight or length. The catch-down growth of high birth weight term infants was not found in the first year of their lives.

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The objective of this longitudinal study is to explore the relationship between temperament and physical development among infants in Beijing, China. A total of 1117 term, normal and singleton infants were followed regularly for 12 months. Body weight and horizontal length were measured at 42 days and monthly from the third to twelfth month of their lives. Infants' temperament was assessed using the revised Chinese infants' temperament scale when the infants were 6 months. There was a significant difference on temperament dimensions between infants' genders (P < 0.05). Infants' weight and length were significantly related to their parents' weight and height. Infants with positive temperaments (easy and intermediate) were heavier than those with negative temperaments (difficult and slow to warm up) (P < 0.05). The horizontal length of boys was related to their temperament categories (P < 0.05). Infants' weight and length were significantly related to their temperament category and parents' weight and height.