Longitudinal Follow-Up Study On Catch-Up Growth Of Low Birth Weightpreterm Infants Aged 0～2 Years

Objective To investigate the growth pattern and characteristics of low birth weight premature infants and full-term infants within 2 years after birth,and to compare the differences between physical growth indicators and WHO criteria and the control group of full-term infants.Methods There were 123cases of low birth weight premature infants and 100 healthy full-term infants.The premature infants were divided into small for gestational age（SGA）group and appropriate for gestational age（AGA）group.There were 88 cases in AGA group and 35 cases in SGA group,all children underwent longitudinal follow-up and intervention management.The data of body weight,body length and head circumference were measured regularly.The Z scores and percentiles were calculated by WHO Anthro software.The data of birth date,the data of measured date and the actual measured growth data were input according to the software requirements.The software automatically output the child’s Z scores and percentiles of body weight,length,head circumference,weight/height（W/H）and body mass index（BMI）.The body weight,length,head circumference,BMI and W/H Z scores and percentiles of the child at 3,6,12,24 months after birth were calculated respectively.Statistical processing:The measurement data were expressed as mean±standard deviation（（?）±s）.The t test and repeated measurement data analysis of variance were used.The composition of the percentile was compared with theχ2 test.Results 1.Body weight,length,head circumference and W/H in preterm infants were lower than those in full-term infants（P<0.05）.BMI reached the highest value in 6 months after birth and gradually declined after 6 months.BMI in full-term infants was higher than that in preterm infants after 6 months（P<0.05）.2.The variance of the original data of preterm infants and full-term infants at each month was measured repeatedly（P<0.05）.Analysis and comparison showed that the body weight,body length,head circumference and W/H value of the two groups showed an overall upward trend.The growth rate of body weight and W/H value was the fastest before 3 months of age,the growth rate of body length and head circumference was the fastest before 6 months of age,and then slowed down.BMI value increased before 6 months old,and decreased after 6 months old.3.The body weight,head circumference,BMI and W/H Z scores of premature infants showed an upward trend within 24 months after birth.The Z-score of body length showed an upward trend within 12 months after birth,but did not increase between 12 and 24months of age.The inter-group effect showed that the Z-scores of body weight,body length and head circumference of preterm infants were lower than those of full-term infants at 3-24 months of age（F=156.29,F=147.22,F=76.391,F=18.654,F=65.587,P<0.05）.4.Compared with SGA group,body weight,body length,head circumference and W/H of AGA infants were higher than SGA group at each month of age.There were significant differences in body weight and body length at each month of age（P<0.05）.There was no significant difference in head circumference,BMI and W/H between the two groups at 6 months after birth（P<0.05 for 12 and 24 months）.5.SGA and AGA were compared by repeated measurements of body weight,body length,head circumference,BMI value and W/H value Z score.The analysis of intra-group effects showed that the body weight,body length,head circumference and BMI value Z score of the two groups showed an overall upward trend,the growth rate was the fastest before 6 months of age,and then slowed down.The W/H value of AGA group increased continuously in 2 years after birth.The Z score of W/H value fluctuated around-0.6 in 2 years after birth in SGA group.There was no significant difference between the two groups.It increased slightly before 6 months,decreased slightly from 6 months to 12 months,and increased again from 12 months to 24 months.The inter-group effect showed that Z score of body weight,body length,head circumference,BMI value and W/H value of AGA group were higher than those of SGA group after birth during 3-24 months.The difference was significant（F=13.254,F=8.575,F=6.902,F=7.904,F=5.953,P<0.05）.The body weight,length and BMI of AGA group at 12 and 24 months old were close to the average level of WHO standard children of the same age.6.Distribution of body weight,body length and head circumference frequency:P_0-25-25 accounted for a large proportion when the body weight and body length of preterm infants were 3-6 months old,and then decreased gradually with the increase of month age.The proportion of head circumference P_0-25-25 did not decrease significantly with month age.Compared with full-term infants of the same age,there were significant differences in the distribution of body weight,body length and head circumference frequency（P<0.05）.Conclusion The body weight,body length and head circumference of low birth weight premature infants catch up with growth within 24 months after birth.The head circumference catch up degree is lagging behind that of body weight and body length.Catching-up growth mainly occurred within 12 months after birth,showing a pattern of rapid growth followed by slow growth.The physical growth of SGA preterm infants at all months of age was lower than that of AGA preterm infants.