Smoking during pregnancy associated with smaller brain volume in child

Smoking tobacco while pregnant can lead to one’s child experiencing lower brain volumes and suboptimal cortical traits, according to a study by The Journal of the American Medical Association (JAMA).

Investigators conducted brain morphology in children aged 9 to 11 years. Over 2700 study participants had been exposed to maternal smoking during pregnancy, and a subsample of 784 patients had recorded DNA methylation. Magnetic resonance imaging (MRI) was used to examine brain volumes and surface-based cortical measures in patients.

Study participants underwent a brain MRI assessment, and it was found that those who were exposed to maternal smoking during pregnancy had a smaller total brain volume (TBV) than those not exposed. Specifically, children who were continuously exposed during pregnancy were observed to have lower TBV levels, and there was less gyrification observed in children exposed to maternal smoking. 

These changes in brain morphology were not found in children who were only exposed early in the pregnancy. Children exposed to maternal smoking in only the first trimester were found to have the same brain morphology as children not exposed at all.

Paternal smoking was shown to have effects as well, with both maternal and paternal smoking leading to a larger putamen in the child by the time they were 10 years of age. There were far more cases of brain morphology reported in cases of maternal smoking, however. No association was made between paternal smoking and changes in the cortical thickness, surface area, or gyrificationof the child.

No proof was found that DNA methylation at birth could mediate the effects of maternal smoking. However, it should be noted that all the children in the DNA methylation subsample were White, and the results cannot be assumed to be the same for other races and ethnicities.

Based on these findings, continuous tobacco use during maternal pregnancy will often lead to complications in the child’s brain developed by the time they are aged 10 years. These complications are seemingly not able to be explained by shared genetics or family factors.

These results are consistent with those of prior studies, which also showed smaller brain sizes in fetuses and children exposed to continuous maternal smoking. For favorable long term brain development in children, the authors encouraged ceasing maternal smoking before pregnancy starts or early in pregnancy.

Reference

Zou R, Boer OD, Felix JF, et al. Association of maternal tobacco use during pregnancy with preadolescent brain morphology among offspring. JAMA Netw Open. 2022;5(8):e2224701. doi:10.1001/jamanetworkopen.2022.24701