Objective      To explore the differences of physical growth trends between preterm and full-term small for gestational age (SGA) infants in the first year.       Methods      Prospective cohort study was adopted to collect 54 preterm SGA infants and 181 full-term SGA infants

who were followed-up at health care department of children's hospital of Chongqing medical university from September 2013 to June 2015. The weight

length

head circumference and growth rate were measured by using Z scores at the ages of 1 month

3 months

6 months and 12 months

and the preterm SGA infants were measured at the corrected gestational ages of 1 month

3 months

6 months and 12 months.       Results      Preterm SGA began rapid catch-up growth after corrected age of 1 month

while full-term SGA began after birth. The catch-up growth rates of preterm and full-term SGA reached to 63% in the first 6 months. There were no significant differences in the weight Z score at the not-corrected gestational age of 6 months and 12 months (t=-1.189

-0.911

P=0.236

0.363)

length (t=-0.855

P=0.394) and head circumference Z score in 12 months (t=-1.078

P=0.282) between the preterm SGA infants and full-term SGA infants. The chasing speed of weight (t=4.685

3.787

P0.01) of preterm SGA was obviously faster than that of full-term SGA during 1~3 months and 3~6 months

and the chasing speeds of length (t=3.487

3.626

4.179

P0.01) and head circumference (t=5.158

3.001

4.641

P0.01) in preterm SGA were obviously faster than those of full-term SGA during 1~3 months

3~6 months and 6~12 months. But the chasing speeds of weight and length of preterm SGA were obviously slower than those of full-term SGA within 1 month (t=-6.384

-4.821

P0.01)

even below the Z score at birth (ΔZ0).       Conclusion      The starting point of catch-up growth of preterm SGA is latter than that of full-term SGA. The physical growth levels of preterm SGA can catch up with full-term SGA at the age of 1 year old. The growth potential of preterm SGA is greater than that of full-term SGA. Extrauterine growth retardation is easier to happen in preterm SGA infants at the corrected age of 1 month.