Smoking while pregnant diminishes baby’s brain size, gray matter

Prenatal tobacco use adversely affects brain development by limiting a child’s total brain volume and particularly their gray matter, according to longitudinal MRI research published in the March 2014 edition of Neuropsychopharmacology.

Hanan El Marroun, PhD, from the department of child and adolescent psychiatry, Erasmus MC, Sophia Children’s Hospital in Rotterdam, the Netherlands, and colleagues conducted the research as part of the population-based Generation R Study that has followed children in the Netherlands from pregnancy onward. This study includes 226 matched children from before birth to follow-up at ages six to eight to assess the developmental effects of prenatal tobacco exposure.

“[E]vidence is accumulating that prenatal tobacco exposure is related to psychiatric disorders and mortality from childhood to young adulthood,” wrote El Marroun et al.  “Thus, having a better understanding of how alterations in the brain due to prenatal exposure to cigarettes contribute to at-risk states in children is important.”

It is well accepted by the medical community that smoking while pregnant is unhealthy for unborn children and has been associated with spontaneous abortion and sudden infant death syndrome, but it is not well understood what the true, long-term morphological effects are on child brain development. A total of 113 children who had been exposed to tobacco use during pregnancy were age- and gender-matched with 113 children who had not been exposed. As a result of this long-range MRI neuroimaging study, researchers were able to ascertain multiple areas of restricted growth and negative emotional and behavioral consequences correlated with prenatal smoking.

“Children exposed to tobacco throughout pregnancy have smaller total brain volumes and smaller cortical gray matter volumes,” the authors wrote. “Continued prenatal tobacco exposure was associated with cortical thinning, primarily in the superior frontal, superior parietal, and precentral cortices.”

Changes in thickness of these structures were linked with affective disorders. Interestingly, children whose mothers stopped smoking during pregnancy showed the same brain development as non-smoking mothers.