Abstract: 　Objective　To explore the relationships of insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 3 (IGFBP-3) with growth of very low birth weight (VLBW) infants in the early postnatal stage. Methods According to the individual gestational age and birth weight, 32 cases of VLBW infants were divided into small for gestational age (SGA) group and appropriate for gestational age (AGA) group. After birth, all the infants were given the same nutritional intake. The body weight, body length, head circumference and body mass index (BMI) were monitored at different time points (d0, d7, d14 and d28 after birth). Serum IGF-1 and IGFBP-3 levels were measured by radiommunoassay, and IGF-1/IGFBP-3 molar ratio was calculated. Results There was no significant difference of body weight, body length, head circumference and BMI between two groups at d0, d7, d14 after birth. Body weight and BMI in SGA group were less than those in AGA group at
d28 after birth (P< 0.05). The levels of IGF-1, IGFBP-3 and IGF-1/IGFBP-3 in SGA group and IGF-1/IGFBP-3 in AGA group did not change with age after birth. The levels of IGF-1 and IGFBP-3 were increased in AGA group after birth. The level of IGF-1 in AGA group at d14 and d28 after birth was higher than that in AGA group at d0 after birth (P< 0.05). The level of IGFBP-3 in AGA group at d28 after birth was higher than that in AGA group at d0 after birth (P< 0.05). The levels of IGF-1 and IGFBP-3 in SGA group at d28 after birth were lower than those in AGA group at d28 after birth (P< 0.05). Conclusions Serum IGF-1 and IGFBP-3 levels in SGA group are lower than those in AGA group. Low levels of IGF-1 and IGFBP-3 may result in growth retardation.