Published online August 1, 2007
PEDIATRICS Vol. 120 No. 2 August 2007, pp. 450-451 (doi:10.1542/peds.2007-1323)
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LETTER TO THE EDITOR

Effects of Multiple Courses of Antenatal Betamethasone on the Auditory Brainstem Responses of Premature Infants: In Reply

Sanjiv B. Amin, MD
Ronnie Guillet, MD, PhD
Division of Neonatology
Department of Pediatrics
Golisano Children's Hospital at Strong
University of Rochester
Rochester, NY 14642

We thank Dr Church for his letter regarding our observational study on the effect of multiple courses of antenatal betamethasone on auditory neural maturation. We are glad to see that he also found no effect on auditory neural maturation after exposure to multiple courses of antenatal betamethasone. These findings provide external validity to our findings. To help Dr Church prepare his manuscript, we have attempted to clarify and answer the questions that he raised.

  1. The median number of betamethasone courses given to the pregnant women in our multiple-course-of-betamethasone group was 3 (range: 2–6). It is possible that the effect on birth weight is dose dependent and may not be seen with 3 courses, as was reported by us.
  2. In general, auditory brainstem response (ABR) waves I, III, and V cannot be detected in all premature infants at a gestational age of ≤32 weeks' as outlined in the methods section of our study. The ABR's interpeak latencies were calculated only if absolute wave latencies required to measure interpeak latencies were available for a particular subject. These interpeak latencies were then averaged and reported in our Table 2. The subjects with ABR types II and III may not have had all 3 (wave I, II, and III) absolute latencies measurable. In this case, interpeak latencies were not measurable; however, the measured absolute wave latencies were reported. For example, for a subject with only absolute wave III identified and measured, interpeak latencies I–III, III–V, and I–V cannot be measured. This explains the difference in the values between calculated interpeak latencies that were derived by using the mean wave I and V latencies and the reported interpeak latencies (shown in our Table 2). The same reason explains the importance of using response types, which takes into account unmeasured absolute and interpeak latencies.
  3. Our Fig 1 has been used in several articles on auditory neural maturation, because it helps readers to understand different response types based on the characteristic of an ABR wave form. Although the subjects for the 2 studies came from the same hospital, the 2 studies were different in primary objectives, recruitment period (1996–1997 vs 1996–1998), number of subjects (186 vs 174), and gestational age of the subjects studied (24–32 vs 28–32 weeks). There was a small overlap, but our Pediatrics study involved additional recruitment, data collection, data entry, and statistical analyses. These differences are evident from the methods section of both the studies. Our Pediatrics study was not a reanalysis of the data collected for the study published in the Journal of Perinatology.

PEDIATRICS (ISSN 1098-4275). ©2007 by the American Academy of Pediatrics




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