Does nicotine exposure during pregnancy increase sudden infant death syndrome?

Does nicotine exposure during pregnancy increase sudden infant death syndrome?
© shutterstock/Svetlana Iakusheva

Infants whose mothers have used snus during pregnancy run three times the risk of sudden infant death syndrome.

According to a comprehensive registry from Karolinska Institutet in Sweden, sudden infant death syndrome is more likely to occur when the mother uses snus, a moist oral tobacco product, during pregnancy.

Sudden infant death syndrome is the sudden, unexpected and unexplained death of an apparently healthy baby. In the UK, around 200 babies die suddenly every year; however, it is rare.

“Fortunately, the incidence of sudden infant death is very low, but we can see that taking snus or smoking while pregnant is associated with an increased risk,” said Anna Gunnerbeck, a paediatrician at the Astrid Lindgren Children’s Hospital and researcher at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet.

Little research on snus and other tobacco products

It is well known that smoking during pregnancy is a risk factor in sudden infant death syndrome; however, little research has been conducted on snus and other nicotine products.

The researchers conducted a registry study comprising over two million babies born in Sweden between 1999 and 2019. During this time, only two out of 10,000 babies suffered sudden infant death, which is when death occurs suddenly for no apparent reason during sleep.

When registered for maternal care, just over 1% of the mothers took snus, and 7% smoked. Taking snus during pregnancy was linked to a 70% increase in the risk of sudden infant death during the first year, regardless of cause, and a three-fold increase of sudden infant death syndrome. The risks associated with taking snus were comparable to moderate smoking (one to nine cigarettes a day). The highest risks were associated with smoking over ten cigarettes a day.

It is important to note that all nicotine products should be avoided during pregnancy, and the risk of quitting tobacco products early in pregnancy lowers the risk of sudden infant death syndrome.

“Given the dramatic rise in the use of snus among young women of fertile age in Sweden over the past few years and the growing popularity of e-cigarettes, women need to be informed of the potential risk to foetuses and infants,” said Dr Gunnerbeck. “Our study indicates that nicotine is a risk factor of sudden infant death, so we conclude that all types of nicotine products should be avoided during pregnancy.”

No established causality discovered

The team linked the different registries to allow adjustments for a number of important potential risk factors of sudden infant death syndrome, such as socioeconomic status and the age of the mother. However, the researchers are unable to establish any causal relationships, since unknown factors might have impacted the results.

It is difficult to separate the risk for the foetus associated with snus and smoking from exposure to cigarette smoke and nicotine in the breast milk after the baby is born. Furthermore, mothers who stopped smoking or taking snus early on in their pregnancy might also have resumed the habit later. The researchers had no information about how much snus was consumed during pregnancy or what dose of nicotine that may cause harmful effects.


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