Smoke exposure affects newborn hearing

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© Konstantin Yuganov / Fotolia

A study from Western Michigan University has found significant cotinine level elevations in mothers who smoked more than 10 cigarettes a day during pregnancy compared to non-smoking mothers. Prenatal smoke exposure has been shown to change cochlear echo response amplitudes and auditory brainstem response (ABR) wave latencies in newborns.

“Since gene expression changes are often synchronized in different tissue types, the goal of the present work was to determine relationships between prenatal smoke exposure induced changes in hearing responses with changes in placental gene expression,” according to researchers.

Cochlear echo response amplitudes in the 2-8 kHz range and ABR wave latencies, specifically wave V and interpeak interval I-V, were also significantly reduced in newborns of smoking mothers. They found other relevant functional pathways were significant at unadjusted enrichment p-values of 0.001-0.11 and included calcium signaling, neurotransmission/neurological processes and oxidative stress.

“These placental genes may mediate active contraction and relaxation in the placental villi, for example, during maternal-fetal perfusion matching, similar to the active lengthening and shortening of the cochlear outer hair cells during sensory transduction,” says their report. “Thus, the functional consequence of their alteration in the cochlea would be reflected as a decline in cochlear echoes as shown in this study.” Such parallel changes suggest the potential utility of placental gene expression as a surrogate for evaluating changes in the developing cochlea related to potential aberrant cochlear function in newborns.

Source: Neurotoxicol Teratol, May 2013

R.S.