Abstract(#br)Background(#br)Intrauterine growth restricted (IUGR) fetuses are those with estimated weight <10th customized centile, displaying signs of chronic malnutrition and hypoxia leading to brain sparing effect. Neurotrophins, [Nerve Growth Factor (NGF), Brain Derived Neurotrophic Factor (BDNF), Neurotrophin-3 (NT-3), Neurotrophin-4 (NT-4)] are important for pre- and post-natal brain development.(#br)Aims(#br)To investigate circulating NGF, BDNF, NT-3 and NT-4 levels in IUGR and appropriate for gestational age (AGA) fullterm fetuses and neonates (day-1 [N1] and day-4 [N4]) and in their mothers.(#br)Study design(#br)Prospective case control study.(#br)Subjects(#br)60 mothers and their single 30 IUGR and 30 AGA fullterm fetuses and neonates.(#br)Outcome... measures(#br)Determination, by enzyme immunoassays, of NGF, BDNF, NT-3 and NT-4 plasma levels.(#br)Results(#br)No statistically significant differences existed between IUGR and AGA maternal, fetal and neonatal levels of BDNF, NT-3 and NT-4. NGF was significantly higher in AGA than IUGR maternal ( p =0.007), fetal ( p =0.01), neonatal day 1 ( p =0.043) and 4 ( p =0.003) plasma, and positively correlated with the infants' centiles and birthweights. IUGR and AGA maternal neurotrophins were higher than the respective fetal and neonatal ones and no correlation with gender or delivery mode in both groups was observed.(#br)Conclusions(#br)In the perinatal period, circulating levels of BDNF, NT-3 and NT-4 do not differ in IUGR and AGA pregnancies, in contrast to NGF levels, which are higher in the AGA group. NGF is the only neurotrophin correlating with customized centiles and birthweights of the infants. Neurotrophin concentrations are higher in maternal plasma and do not depend on gender.