Brainstem auditory evoked potentials (BAEPs) in pregnant women

The electrophysiological correlate of change in sensory function during pregnancy has not been reported. The brain stem auditory evoked potentials were recorded in eight pregnant women during third trimester from CZ-A1 and CZ-A2 position, with alternating 90 dB sound pressure click stimuli delivered at 10/sec and -40 dB (white noise) masking of contralateral ear. Two thousand and forty eight responses were analysed and replicated. The noise and other artefacts were rejected with filter bandpass setting 150 to 3000 Hz. The evoked responses in pregnant women were compared with ten age matched normal subjects using Student's 't' test. The threshold for eliciting wave V of the brainstem auditory response was higher in pregnant women (28.1 +/- 2.1 dB). The absolute peak latencies of waves I to V were similar in both groups. However, Inter peak latencies (IPLs) I-III, III-V were on higher side in the pregnant women, and I-V, in particular (3.9 +/- 0.14) was significantly higher when compared with controls (3.73 +/- 0.16). These findings suggest that besides an increase in evoking wave V threshold, neural conduction process in brainstem auditory pathways during pregnancy is also delayed within + 2SD of the mean central conduction time in nonpregnant state.