US researchers have found altered sleep patterns amongst breastfed infants of mothers who smoke. Julie Mennella from the Monell Chemical Senses Centre in Philadelphia recruited 15 breast feeding mothers who smoked. Sleep and activity patterns in their babies, which were aged between 2 and 6 months, were monitored on two occasions over a three hour period after the children were fed. On both occasions the mothers were asked to abstain from smoking for 12 hours before the study, but on one of the two occasions they were allowed to smoke just before they fed their babies. The women were also asked to avoid caffeinated drinks during the study. Tests on the milk from mothers who had recently smoked confirmed that the babies were receiving a significant increase in nicotine dose, and the team found that the amount of sleep taken during the following three hours by these babies fell from an average of 85 minutes to 53 minutes, a drop of almost 40%. This is probably due to the neuro-stimulatory effects of nicotine, which has been show to inhibit regions of the brain which are concerned with controlling sleep. It may also, suggests Manella, explain why neonatal nicotine exposure has been linked in the past with long-term behavioural and learning deficits, since these could be the consequence of sleep disturbance. In the light of these findings, mothers who smoke might want to consider planning their smoking around their breast-feeding. Nicotine levels in milk peak 30-60 minutes after smoking, but take 3 hours to return to baseline, so this might be feasible.