The fetal origins hypothesis states that nutritional deprivation in utero affects fetal development and contributes to the incidence of diseases associated with the metabolic syndrome in later life. This study investigated whether haemoglobin (Hb) A(1c), an indicator of blood glucose, varied among healthy male adolescents according to their fetal growth rate, in a middle-income setting. Participants were men aged 18 years, belonging to the 1982 Pelotas birth cohort. Complete data, including gestational age and Hb A(1c) at age 18 years, were available for 197 individuals. There was an inverse association between mean Hb A(1c) and birthweight for the gestational age, but not birthweight alone. The association remained significant after adjustment for family income and mother's education, as well as for body mass index at 18 years (P for trend=0.01 and 0.03, respectively).