Ghrelin is a newly discovered orexigenic peptide originating from the stomach. Circulating ghrelin levels reflect acute and chronic energy balance in humans. However, it is not known whether ghrelin also plays a role in energy homeostasis during fetal life. Forty-one small-for-gestational age (SGA) and 34 appropriate-for-gestational age (AGA) infants were studied in order to determine whether cord blood ghrelin concentrations were different in SGA infants compared with AGA infants and the relationship to anthropometric measurements at delivery. The cord blood ghrelin concentrations of SGA infants (means +/- S.E.M.; 15.20 +/- 3.08 ng/ml) were significantly greater than of AGA infants (2.19 +/- 0.24 ng/ml) (P < 0.0001). They were negatively correlated with the infants' birth weights (r = -0.481, P < 0.0001) and with body mass index values (r = -0.363, P < 0.001). The higher ghrelin concentrations were found in female infants (20.42 +/- 4.55 ng/ml) than in males (7.05 +/- 2.27 ng/ml) in the SGA group (P = 0.042). These data provide the first evidence that cord ghrelin levels of SGA infants are greater than those of AGA infants and it is suggested that ghrelin is also affected by nutritional status in the intrauterine period.