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Auditory brainstem responses (ABRS) in neonates exposed to repeated courses of antenatal corticosteroids

      Objective

      The neonatal ABR, a sensitive measure of brain maturation, can help determine if repeated courses of antenatal corticosteroids (AC) had a beneficial or harmful effect on infant brain and auditory function. Our objective was to determine if repeated AC had any effects on the neonatal ABR.

      Study design

      We performed an ancillary study at 6 of the 19 centers that conducted a double-blind, placebo-controlled clinical trial of repeated AC. Consenting women <32 wks gestation, who were at high risk for preterm birth and had received one course of AC, were randomized to receive additional weekly courses of AC (Betamethasone) or placebo. ABR testing was performed on infants prior to discharge. The ABRs were evoked by 45 and 70dB clicks delivered to the right and left ears separately, utilizing standard procedures and recording equipment. The ABR's Wave V latencies were analyzed by the Wei-Lachin procedure which adjusts for the correlation due to twins (P < .05 considered significant, 2-tailed test).

      Results

      We enrolled 49 mothers, 11 of whom carried twins, giving 60 infants who were ABR tested. Fifty-one infants had complete sets of ABR data. The repeated AC (n = 24) and placebo (n = 27) groups respectively had right ear Wave V latencies (mean ± SD) of 7.93 ± 0.60 vs 7.63 ± 0.65 msec (P = .08) and left ear Wave V latencies of 7.73 ± 0.60 vs 7.62 ± 0.52 msec (P = .41) – where longer latencies suggest less maturity. A power analysis (80% power), using an infant's highest Wave V latency value from either ear, indicated that a total 260 infants (130/group) would be needed to achieve statistical significance. Results from the 45 dB condition were very similar. The number of treatment courses, gestational ages at birth and at ABR testing did not differ between groups; whereas birth weight, head circumference and length were smaller in the repeated AC group (P < .05).

      Conclusion

      Repeated AC treatments did not affect neonatal brain development as assessed by the ABR's Wave V latencies, despite significant effects on birth size.