High copeptin concentrations in umbilical cord blood after vaginal delivery and birth acidosis

Context: The pituitary-secreted nonapeptide arginine-vasopressin (AVP) is unstable and therefore unsuited for diagnostic use, but its secretion can be estimated by measuring copeptin, the C-terminal portion of the AVP precursor (pro-AVP). Objective: Our objective was to investigate perinatal factors affecting copeptin concentrations in infants at birth and at 3 d of life. Design and Setting: We conducted a prospective cross-sectional study at a tertiary university hospital. Patients: Copeptin plasma concentrations were evaluated in 177 infants at birth, including 117 paired arterial/venous umbilical cord and 102 venous blood samples obtained at 3 d of life. Main Outcome Measure: Copeptin concentrations were determined by a C-terminal pro-AVP luminescence immunoassay. Results: Arterial umbilical cord copeptin concentrations were consistently higher than matched venous ones (median 18 vs. 10 pmol/liter, P < 0.001), but both values were closely related (Rs = 0.825; P < 0.001), and both were negatively relate...