[Real world research on the growth pattern of preterm children with different birth weight]

Objective: To investigate the physical indices and growth status of preterm children aged 0 to 4 years with different birth weight. Methods: Following the real world research approach, the current study retrospectively collected e-chart information of 8 496 preterm children from the child health care system of the Children's Hospital of Chongqing Medical University from December 2010 to December 2017, with 203 123 full-term children followed up during the same period as controls. Premature children were divided into normal birth weight (NBW) group, low birth weight (LBW) group, and very low birth weight (VLBW) group based on their birth weights. The weight and length development within 48 months of age of preterm boys and girls in each group were measured and recorded to establish a numerical table and analyze the growth levels, growth rate, and proportionality. The t-test or chi-square test was used for between-group comparison. Results: Of the 8 496 preterm children, 4 839 were girls and 3 657 boys, including 525 in the VLBW group, with an average birth weight of (1.28±0.14) kg, 3 862 in the LBW group, with an average birth weight of (2.07±0.28) kg, and 4 109 in the NBW group, with an average birth weight of (2.86±0.35) kg. The weight at the actual age of 2-<3 months ((5.61±0.96) vs. (5.64±0.78) kg in boys, (5.11±0.67) vs. (5.18±0.71) kg in girls) and the length at the actual age of 8-<10 months ((70.3±2.4) vs. (70.6±2.4) cm in boys, (68.9±2.2) vs. (68.9±2.4) cm in girls) in the NBW group reached the average weight and length of full-term children. The difference of physical growth before 24 months of age between LBW and control group decreased as children age, with that of LBW group approaches the average of full-term children after 24 months of age, with a weight difference of 0.64-0.95 kg and height difference of 1.3-1.7 cm. The weight and height of the VLBW group were lower than those of full-term infants (2.80-2.86 kg and 3.3-4.3 cm, respectively) at 48 months of age. During 2-12 months of age, the corresponding values of the VLBW group were higher than that of the LBW and NBW groups by 0.35 kg and 0.71 kg, respectively. However, the corresponding values of the VLBW group were lower than that of the LBW and NBW groups(0.64 kg and 0.76 kg at 0-2 months of age, 1.04 kg and 1.49 kg at 12-48 months of age, respectively). The rates of delayed development, underweight, and emaciation were the highest in the VLBW group (all P<0.01), while the rates of overweight and obesity were the highest in the NBW group, with that of the VLBW group being lower than LBW group (P<0.01) at the age of 24-<36 months. Conclusions: Prior to 4 years of age, the time for preterm children to reach the average physical indices of full-term children differ by birth weights, hence warranting further examination of the corrected gestational age for preterm children. Normal birth weight preterm children present with the highest incidence of overweight and obesity and very low birth weight preterm children present with the highest incidence of growth disorders, marking both groups at high risks of malnutrition.