Smoking during pregnancy raises odds of overweight children

The risk is linked to changes in infant gut bacteria, study shows.

EDMONTON — Smoking during pregnancy changes the gut bacteria in the infant, according to a recent study in the journal Gut Microbes that associates this development to an increased risk of the child becoming overweight or obese.

Childhood obesity is a growing concern globally, affecting more than 18 per cent of children and adolescents aged five to 19 in 2020, a startling increase from just four per cent back in 1975. 

University of Alberta co-senior author of the study, Anita Kozyrskyj, and her team used data collected from more than 1,500 children that documented the mothers’ environmental and lifestyle factors during and after pregnancy. Weight outcomes of the children were also measured at one and three years of age, and stool samples were collected and analyzed at three and 12 months of age.

The researchers found that an increased risk of children being overweight and obese was associated with the amount and diversity of a specific bacteria known as Firmicutes. While a normal part of our gut bacteria, Firmicutes were present in higher amounts and occurred too soon in the guts of infants whose mothers smoked during pregnancy.

Kozyrskyj explains that the excessive levels of Firmicutes can result in excessive production of butyrate, a short chain fatty acid and natural byproduct. “It’s not like butyrate is poisonous or anything like that. It’s a natural byproduct. We have butyrate levels in our intestines all the time,” she says. But again, her team observed earlier and higher levels of butyrate among infants of smoking moms.

This study doesn’t indicate a direct cause and effect between too much butyrate in infants and them becoming overweight, but rather an association — emphasizing the need for public health initiatives aimed at encouraging women to stop smoking before becoming pregnant.

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To speak with Anita Kozyrsky, please contact:

Debra Clark
University of Alberta communications associate