Smoking while pregnant could risk child's hearing

Women who smoke when they are pregnant and after giving birth may risk damaging their children's hearing, a study suggests.Nicotine exposure before birth and during breastfeeding can cause a sound processing area of the brain to develop abnormally, results from a mouse study show.

The research is the first to demonstrate that the auditory brain stem is vulnerable to damage from nicotine.Children with impaired function in this segment of the brain are likely to experience problems with language development and learning difficulties.

German scientists added nicotine to the drinking water of pregnant mice at levels equivalent to heavy smokers.

When the offspring were born, the firing and signalling ability of neurons in their brains was tested - compared with unexposed offspring, neurons sensitive to input from the inner ear were less good at transmitting signals.

The signals they did transmit were less precise, so the coding of sound patterns was disrupted, the findings published in The Journal of Physiology showed.

Lead researcher Professor Ursula Koch, from the Free University of Berlin 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 brain stem.

"If mothers smoke during pregnancy and their children show learning difficulties at school, they should be tested for auditory processing deficits."

Nicotine exposure during pregnancy was already known to harm the brain development of foetuses, and mothers are at increased risk of premature delivery, and sudden infant death.