Secondhand Smoke Exposure: No Level Is Safe in Pregnancy

You likely already know that smoking while you’re pregnant or have a newborn in the house can adversely affect your and your baby’s health. Smoking can also increase your risk of severe COVID-19 disease, which if you’re pregnant or have a new baby is already more dangerous. What you may not know is that even if you are not a smoker yourself, if you’re around people who are smoking, it can create problems for you and your baby.

In a 2018 study published in the journal Preventive Medicine Reports, Bernard Fuemmeler, a public health researcher at the Virginia Commonwealth University Massey Cancer Center, and colleagues found that pregnant people who are younger and are earlier in their pregnancy—that is, so early that they might not even know they are pregnant—are more likely to be exposed to secondhand smoke. Secondhand smoke exposure during pregnancy is associated with several poor outcomes, including low birth weight and stillbirth.

Fuemmeler and his team have now recognized a possible reason behind the detrimental effects of secondhand smoke exposure. In a new study, published in May in the journal Environmental Health Perspectives, the researchers showed that secondhand smoke exposure is associated with changes to the modifications on and packaging of a newborn’s DNA—the material in every cell in the body that’s inherited from a person’s parents and tells the cells how to be part of a human being.

When changes to how the DNA is marked or packed into a cell happen, they may disrupt how the cell acts, what products it makes, and how it behaves in the body. The authors of the study determined that many genes were affected in the DNA of babies whose mothers were exposed to secondhand smoke, including genes related to the development of the brain.

Scientists already knew that smoking while pregnant is linked with these types of changes to DNA packaging. This work points to the fact that a similar link exists between these changes and secondhand smoke exposure and suggests that “no level of smoke exposure is safe during pregnancy,” as Fuemmeler explained in a press release about the work from the Massey Cancer Center.

In the study, the authors emphasize the importance of policies that help keep places where pregnant people may be smoke-free. “It’s important not only for our homes, but also in the environment,” Fuemmeler said in the press release. “Clean air policies limit smoke in public, and for pregnant women that may have long-term effects on offspring.”

If you are someone who is exposed to secondhand smoke by family members or coworkers, consider asking them to help you limit your exposure. Smokers in your life should always smoke outside and not in close physical proximity to you. When they come back inside, they should change clothes and thoroughly wash their hands and face.

If you encounter secondhand smoke as part of your job or home environment, think about how to address the issue with people in charge, especially while you are pregnant. If you encounter secondhand smoke in your job, speak to the smoker or to a supervisor about limiting your exposure. Employers are within their rights to ban all smoking at work, which may be a possibility at your workplace. If you’re exposed to secondhand smoke via your home, perhaps in a shared living situation such as an apartment building, look at your lease. It is possible that there is a clause forbidding smoking, in which case you can address the issue with the manager of your building or the landlord. Even if your lease does not contain such a clause, there still may be things that your landlord can do to limit your exposure, including moving the smoker elsewhere and installing better seals around doors and windows of your home.

Finally, it makes sense, while you are pregnant, to avoid places where you may be around smokers, including restaurants and bars that allow smoking and concert venues, particularly those that allow smoking indoors. According to the US Centers for Disease Control, ventilation doesn’t effectively protect nonsmokers from being exposed to secondhand smoke and there is no risk-free level of exposure, so it’s best to visit public spaces that completely prohibit smoking.

Abby Olena
Dr. Abby Olena has a PhD in Biological Sciences from Vanderbilt University. She lives with her husband and children in North Carolina, where she writes about science and parenting, produces a conversational podcast, and teaches prenatal yoga.

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