Maternal smoking cessation study reveals ‘inheritable’ impacts on child development

Written by: Tim Brouk,

Valerie Knopik

Valerie Knopik

In 2020, the Centers for Disease Control and Prevention reported that in the United States “5.5% of all births were to women who reported smoking cigarettes at any time during pregnancy.” That translates to almost 200,000 children who were at risk for cognitive and physical development issues from the effects of cigarette use.

Valerie Knopik and Kristine Marceau, professors in the Purdue University Department of Human Development and Family Science, analyzed the effects of maternal smoking on pairs of siblings within 173 Missouri families. Along with graduate students Amy Loviska and Li (Hazel) Yu, the team wanted to see how siblings in the same family performed in executive function tasks when one was born when the mother smoked during pregnancy and the other child was born when the mother was not smoking or smoked less. Would one child perform activities related to memory, self-control or paying attention to stimuli better because the mother did not smoke while pregnant with them?

In the cases of children ranging from ages 8-15 who were born between 1998-2005, some executive functions were performed better by the sibling where the mother did not smoke, according to the study. One working memory task and one response inhibition task were performed better by the children who did not experience maternal smoking as a fetus. The more surprising aspect of the study: The results of the other executive function tasks suggested similar performance for both siblings regardless of prenatal exposure. Knopik, Marceau and their team concluded a mother’s smoking cessation is a crucial factor in her child’s development but not the only risk: secondhand smoke must be considered as well as many socioeconomic factors. Genetics also play a key factor.

“Many of these outcomes showed an inheritable component that runs in families,” said Knopik, who was named president of the Behavior Genetics Association this summer. “That could be due to genetics, the environment the family creates or a combination of the two.”

Kristine Marceau

Kristine Marceau

Show-Me the data

The Missouri data is an extension of Knopik’s research that began when she was junior faculty at Washington University in St. Louis. The Missouri Mothers and Their Children study focused on families from households where the mother admitted to smoking while pregnant with one child but did not smoke (or smoked less) with the other child. As part of the study, the mother, father and children were interviewed, and the entire family participated in two-to-four-hour neuropsychological testing sessions.

“We decided to have the age of the younger sibling go to only 8 years old because we wanted them to be able to complete some of the tasks we were interested in,” Knopik explained. “We wanted the individuals to be through the period of risk of having ADHD diagnoses as well, which at the time was around 7 years old.”

Socioeconomic importance

Marceau said the study highlighted how intertwined smoking behaviors are with other challenges families face, especially if they suffer under socioeconomic hardships. In other words, a mom can likely quit smoking a lot easier than digging out of a societal cycle of poverty where she doesn’t have to work two or three jobs to support her children. Digging deeper into the literature, the researcher found numerous factors that can impact children — from secondhand smoke from the father or other family members to lack of socioeconomic resources. Mothers’ own cognitive abilities are also important — these factors all can impact interest or means for reading or playing games that can improve a child’s cognitive development.

“They’re all interrelated,” Marceau said. “Of all the things we put in the model, what was more important were those correlated familial problems than smoking during pregnancy itself.”

Another sobering fact, while the percentage of mothers who admitted to smoking during a pregnancy may seem high, it’s most likely even higher, as some pregnant women were most likely not forthright in their smoking habits.

“We think that those rates are actually low,” Knopik said. “It’s really interesting at the extent smoking while pregnant still happens.”

The study reinforced that parents have a lot to consider when raising a family. Moms quitting smoking is a tremendous, required first step, but more work must be done in the household for ideal child development.

“A lot of these things are inheritable. The parents are also creating an environment that the kids are living in,” Knopik said. “The reality is that it’s a much more complex and dynamic constellation of things that is contributing to what you’re seeing in the children, the problems that they’re experiencing.”