A number of medical studies now indicate that maternal smoking during pregnancy can permanently affect brain development, inhibiting the growth of neurons. Nicotine may also alter alter the brain biochemistry by altering DNA and RNA synthesis. Children of mother who smoke during pregnancy have higher rates of neurobiological difficulties, including inattention, impulsivity, and hyperactivity. I would surmise that smoking during breastfeeding would continue the nicotine exposure and might contribute to some of these biochemical changes. (Although the other benefits of breastfeeding might offset some of these negatives significantly.) Smoking in the household has been shown in a large number of studies to be associated with markedly increased rates (6-10 times increased) of wheezing, asthma development, otitis media, bronchiolitis, chronic bronchitis, and URI's in children exposed to smoke; the effects are dose-dependent. It takes about 2 weeks to completely clear secondhand smoke from a room once it's been smoked in. Therefore, parents (and other relatives/friends/etc.) who are nicotine addicts (and nicotine IS an addictive drug) should smoke outside. Maybe some of this information can be used to help convince nicotine-addicted moms (and dads) that their smoking is very harmful to their baby and help them decide to quit (or at least smoke outside). It is still better for the infant to be breastfed by a smoking mom than not to be breastfed at all, however, since an artificially-fed infant has even more health risks. Linda L. Shaw MD FAAP