Amniotic fluid S100B protein and erythropoietin in pregnancies at risk for fetal hypoxia

ObjectiveS100B protein is a biochemical marker for brain injury, and high serum S100B levels have been observed in newborns with birth asphyxia. We hypothesized that the concentration of amniotic fluid erythropoietin, which increases in chronic fetal hypoxia, correlates with amniotic fluid S100B concentration.Study designAmniotic fluid samples in 35 pregnancies at high risk for chronic fetal hypoxia were obtained at cesarean section or by amniocentesis done within a median of 2 days before delivery. S100B and erythropoietin concentrations were measured by chemiluminescent immunoassays.ResultsA positive correlation existed between the concentrations of S100B and erythropoietin in the amniotic fluid (r = 0.57, p < 0.0001). Amniotic fluid S100B concentration was higher (70 ng/l; 33–469, n = 17) (median; range) in pregnancies with elevated amniotic fluid erythropoietin (≥50 IU/l) than in pregnancies with normal erythropoietin (34 ng/l; 20–340, n = 18) (p < 0.0001, Mann–Whitney U-test). S100B predicted an elevated amniotic fluid erythropoietin concentration in the study population with the sensitivity of 94% and specificity of 83%.ConclusionA strong positive correlation exists between amniotic fluid S100B and erythropoietin concentrations in pregnancies at high risk for chronic fetal hypoxia. This suggests that chronic fetal hypoxia increases the intrauterine release of S100B.