Monitoring pudendal nerve function during labor

To determine methodology and feasibility of pudendal nerve monitoring during labor and delivery.

With Institutional Review Board approval, 13 low-risk, singleton pregnant women were recruited. The latency and amplitude of the perineal branch of the pudendal nerve compound muscle action potential were recorded during the second stage of labor and after delivery. With the first two patients, a wire electrode was used to stimulate the pudendal nerve continuously at the ischial spine. For the remaining 11 patients, a St. Mark's electrode was used to stimulate transvaginally. Aurethral ring electrode on a 14 French foley catheter monitored the response from the urethral sphincter. All patients received prophylactic antibiotics.

Twelve patients delivered vaginally, and one by cesarean. In two patients, continuous wire stimulation showed a gradual decrease in amplitude. Changes were minimal over 15-minute intervals. Wire electrode placement was technically difficult and dislodged easily. With the remaining 11 patients, all had data available for interpretation, and of the 85 potential perineal branch of the pudendal nerve compound muscle action potentials, 53 were obtained. No patients developed cystitis.

Intrapartum assessment of pudendal nerve function is feasible. Continuous wire stimulation is technically more difficult and does not provide additional information beyond that available from intermittent stimulation.