Background: Growth factor-binding proteins influence the growth of infants starting in utero. Adaptation of the fetus to an adverse uterine environment is associated with changes in the growth hormone-growth factor-insulin axis. Aims:To evaluate serum levels of IGF-I and IGFBP-3 in small and appropriate for gestational age newborn infants. Methods:Fifty-four newborn infants, small (SGA, ns28) or appropriate (AGA, ns26) for gestational age were matched by gestational age and sex. Blood was collect-ed on the first day of life, and anthropometric measure-ments were taken at birth. The serum levels of IGF-I and IGFBP-3 were compared, and correlated with the anthro-pometric measurements. Results:On the first day of life, mean serum IGFBP-3 levels were significantly lower in SGA babies and corre-lated with weight, length, head circumference, and pon-deral index (weight/length 3) (P-0.0001). In contrast, no associations were found between IGF-I serum levels and these anthropometric measurements. Conclusion:Our data show that SGA babies have sig-nificantly reduced IGFBP-3 concentrations at birth.