Current perception threshold increases during pregnancy but does not change across menstrual cycle.

It is well known that pregnancy reduces anesthetic requirements in response to various noxious stimuli. However, there have been no detailed reports concerning functional changes in nerve fibers during pregnancy. Using a Neurometer, a recently available commercial quantitative sensory monitor, we measured current perception threshold (CPT) values for three frequencies corresponding to the stimulation of A-beta, A-delta and C fibers on the median nerve in women at several stages: late pregnancy, the follicular phase and the luteal phase.