A longitudinal study of brainstem auditory response from birth to late term in late preterm babies and abnormal findings in high-risk babies

Objectives: The objective of this study was to examine brainstem auditory function in late preterm babies from birth to late term and detect abnormality in high-risk babies. Methods: A total of 125 babies born at 33-36 weeks' gestations were studied by longitudinally recording brainstem auditory evoked response from birth to postconceptional age (PCA) 42 weeks. The data were compared between 88 babies who had various perinatal problems (high-risk group) and 37 babies who had no major perinatal problems (healthy group). Results: As PCA increased from 33 to 42 weeks, all wave latencies and I-V interpeak interval in brainstem auditory evoked response were decreased, while all wave amplitudes were increased in these babies. At PCA 33-34 weeks, wave III and V latencies and I-V interval in the high-risk late preterm babies were significantly longer than those in the healthy late preterm babies (P<0.05-0.01). At PCA 35-36 weeks, both V latency and I-V interval were significantly longer than those in the healthy babies (P<0.05 and 0.01). During the term period (PCA 37-42 weeks), these differences became smaller with increasing age. The wave V latency and I-V interval in the high-risk babies were significantly longer than those in the healthy babies at PCA 37-38 and 39-40 weeks (all P<0.05), though not significantly at PCA 41-42 weeks. The amplitudes of waves I, III, and V all tended to be smaller than those in the healthy babies. Conclusions: During early life, brainstem auditory function is abnormal in high-risk late preterm babies. The abnormality is most significant at early preterm, improves with increasing age and approaches normal at late term.