Tobacco Effects Fetal Brain

A study recently published in the Journal of Pediatrics provides more evidence of the adverse effects of tobacco use during pregnancy. There is already evidence showing that prenatal tobacco exposure is associated with neuro-cognitive effects in the first 3 years of life, including problems with attention and regulation of emotions. We also know that maternal smoking is linked with intrauterine growth restriction and decreased neonatal birth weight. Now, a study from Finland has shown a link to actual brain development.

The researchers looked at 232 infants from a single hospital from 2001-2006 who were either very low birth weight or below 32 weeks gestational age. The developing fetuses were evaluated with head ultrasounds at different points and brain magnetic resonance imaging at term. 42 of the mothers smoked during their pregnancy (18.1%) and averaged 10 cigarettes per day. This smoking rate of 18% is very similar to what is found in the United States. Mothers who smoked during pregnancy were twice as likely to drink than those who did not smoke. The findings were that infants exposed to prenatal smoking had smaller frontal lobe and cerebellar volumes. The investigators did not report on developing functioning of the children as they aged so no clear clinical implications can be drawn from lower frontal lobe and cerebellar volumes but this study is one more piece of evidence that prenatal exposure to tobacco is clearly harmful.

Thought for the day

" So come what may, I'll not upset my cheerful happiness of mind. Dejection never brings me what I want; my virtue will be warped and marred by it".

The Way of the Bodhisattva

Prenatal Tobacco Exposure Neurodevelopmental

We have known for some time that tobacco use during pregnancy is not a good idea. One of the consistent findings has been the association with tobacco use and low birth weights. Low birth weights are a nonspecific factor that correlates with fetal growth retardation which can occur from a variety of different factors. Tobacco use is one of those. Three studies recently presented at the 56th annual meeting of the American Academy of Child and Adolescent Psychiatry suggest longer term neurodevelopmental problems.

These three studies are all prospective studies. These were not chart reviews looking for correlating factors but involved looking directly at children and their behavior. The first study enrolled 304 women before their fourth month of pregnancy. Self reports were used to assess smoking during pregnancy. The investigators examined the newborn children 1-3 days after birth and at weeks 2 and 4 looking at reflex assessments, orientation to audio and visual stimuli and response to stressors. The infants of mother's who smoked were less attentive and exhibited consistently more irritability. This is consistent with previous findings that suggest some tobacco withdrawal symptoms do occur.

The second study involved 207 infants from the first study evaluated at 6 months of age. The infants exposed to tobacco prenatally showed lower attention spans than non exposed infants.

A third study evaluated self regulation and executive control in a different population of 237 otherwise normally developing three year olds. Those exposed to tobacco prenatally showed poorer ability to wait for a reward and to regulate motor behavior. While Attention Deficit Hyperactivity Disorder (ADHD) is not diagnosed in preschoolers these findings are similar to the problems that do show up in children with ADHD. The study is ongoing and will follow these children on an ongoing basis.

These three studies suggest that smoking during pregnancy is related to attention and self regulatory problems at multiple points of development. Given that about 20% of expectant mothers smoke a large number of children are affected. Tobacco cessation is difficult but perhaps these findings may increase the motivation to quit in women who smoke during pregnancy.

Thought for the day

Tobacco use during pregnancy is simply not a good idea.