London, Feb 13 (IANS): Babies exposed to nicotine before and after birth may be at an increased risk of developing hearing problems due to abnormal development in the auditory brainstem, researchers have found.

The findings showed that the auditory brainstem -- an area of the brain which plays a role in analysing sound patterns -- may have abnormal development in kids when pregnant mothers are exposed to nicotine before and after giving birth.

Children with impaired auditory brainstem function are likely to have learning difficulties and problems with language development.

"If mothers smoke during pregnancy and their children show learning difficulties at school, they should be tested for auditory processing deficits," said lead author Ursula Koch, professor at the Free University of Berlin in Germany.

For the study, published in The Journal of Physiology, the team exposed the offspring of the mice to nicotine before birth and via the mother's milk until they were three weeks old -- an age that is approximately equivalent to primary school children.

Analysing the brains of the mice offsprings, the researchers found that neurons that get input from the cochlea -- sensory organ in the ear -- were less effective at transmitting signals to other auditory brainstem neurons in mice exposed to nicotine.

Moreover, these signals were transmitted with less precision, which deteriorates the coding of sound patterns. These could be part of the underlying causes for auditory processing difficulties in children of heavy smoking mothers, the researchers said.

"We do not know how many other parts of the auditory system are affected by nicotine exposure. More research is needed about the cumulative effect of nicotine exposure and the molecular mechanisms of how nicotine influences the development of neurons in the auditory brainstem," Koch said.