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

Area of Science:

• Neuroscience
• Obstetrics
• Anesthesiology

Background:

• Pregnancy is known to reduce anesthetic requirements.
• Functional changes in nerve fibers during pregnancy remain under-reported.
• Quantitative sensory testing can assess nerve fiber function.

Purpose of the Study:

• To investigate functional changes in nerve fibers during pregnancy.
• To compare nerve fiber conduction between pregnant and non-pregnant women.
• To assess the influence of the menstrual cycle on nerve fiber function.

Main Methods:

• Quantitative sensory testing using a Neurometer.
• Measurement of current perception threshold (CPT) values at three frequencies.
• Stimulation of A-beta, A-delta, and C fibers via the median nerve.
• Inclusion of women in late pregnancy, follicular phase, and luteal phase.

Main Results:

• Significant differences in CPT values for A fibers were observed between pregnant and non-pregnant women.
• No significant differences in CPT values were found across the menstrual cycle (follicular vs. luteal phases).
• CPT values increased in myelinated fibers during pregnancy, indicating altered nerve conduction.

Conclusions:

• Pregnancy alters nerve fiber conduction, evidenced by increased CPT values, especially in myelinated fibers.
• These findings support the theory of pregnancy-induced changes in nerve fiber function.
• Nerve conduction, as measured by CPT, does not appear to change significantly across the menstrual cycle.