Newborns may be more stressed if mother chooses to smoke during the pregnancy, researchers are reporting this month.

Prenatal smoking has been linked to behavioral problems, ADHD, irritable behavior, drug dependence and criminal activity. This study proves there are even more risks to add to the ever growing list.


The nicotine seems to be the source of the negative effects on newborns. Nicotine is a drug that causes dependence with regular use. It is also the reason quitting smoking is so difficult for expectant mothers. However, according to this study, the nicotine may not be the only problem.

Brain Activity

When women smoke while pregnant, they exhibit a reduction in monoamine oxidase A (MAO-A) activity in the brain. The low MAO-A levels may lead to a reduction in brain neurotransmission which could be linked to the behavioral disorders in children born to smoking mothers. These MAO-A levels have nothing to do with nicotine.

Researchers compared the MAO-A levels in the blood of both the women who smoked and their recently born fetuses to the MAO-A levels in mothers who did not smoke. The levels in the smoking mothers and their children were both lower than normal levels.

The newborns were also tested for comfortability after birth and the babies born to smoking mothers tended to be less comfortable for at least 48 hours after birth. Doctors believe this information is a crucial link to the effect smoking has, biologically, on the unborn fetus. Dr. Ivan Berlin, a corresponding author on the study, stated the lower MAO-A levels "may have implications for future research because it proposes a biological explanation for the previously demonstrated relationship between smoking during pregnancy and behavioral disorders in the offspring."

It is inevitable that smoking causes harm to the infant and this study reinforces the need for smoking prevention and cessation programs in the female population of child-bearing age.

Biological Psychiatry - October 2009