"Other investigators measured increases in fetal plasma concentrations of cortisol, β-endorphin, and noradrenaline associated with intrauterine needling procedures, finding that increases during blood sampling from the hepatic vein were greater than those during sampling from the umbilical cord. However, these neuroendocrine responses do not constitute evidence of fetal pain, because the autonomic nervous system and hypothalamic-pituitary-adrenal axis mediate them without conscious cortical processing. Additionally, these responses are not specific for painful stimuli. Plasma noradrenaline concentrations may increase after umbilical cord transfusion, and plasma β-endorphin concentrations may increase after repeated cordocenteses. Plasma cortisol and β-endorphin concentrations increase during innocuous activities such as exercise. Moreover, in adults, neuroendocrine stress responses may persist despite well-controlled postoperative pain. Vital signs also have been used to assess neonatal pain."