Exposure to Thirdhand Smoke Harms the Health of Pregnant Women

A team of researchers from China and the US found that any kind of tobacco smoke–whether from actively smoking or from exposure to secondhand or thirdhand smoke from someone else’s smoking–harmed pregnant women’s health.

By Leta Dickinson

February 18, 2022

Pregnancy is a uniquely vulnerable stage of life. The mother’s immune system changes to accommodate the growing baby, and the baby’s immune system is developing and premature, even after birth. Tobacco smoke is a known hazard for pregnant women and children. Even if pregnant women never smoke, secondhand and thirdhand tobacco still pose a health risk. One study of thirdhand smoke exposure in pregnant mice found that the exposed male mice offspring had lower birth weights, immune system impairment, and possible increased cancer risk. There is also evidence that thirdhand smoke may reduce a mother’s breast milk. Given these harms, it is crucial that pregnant women are not exposed to firsthand, secondhand, or thirdhand smoke.
Unfortunately, smoking rates in mainland China remain high, especially among men, thereby increasing the risk of exposure for pregnant women. In an effort to better understand this risk, a diverse team of researchers from China and the US measured pregnant women’s tobacco smoke exposure and compared it with their perceived health. They found that pregnant women who were exposed to any type of tobacco smoke—first-, second-, or thirdhand—had lower perceived health-related quality of life (HRQoL).
Between August and September of 2019, the researchers surveyed over 15,000 pregnant women between the ages of 16 and 50 from seven regions of mainland China with a web-based survey. They used validated questionnaires to measure tobacco exposure and HRQoL. The HRQoL measures included five dimensions of health: mobility, self-care, usual activity, pain or discomfort, and anxiety or depression
Women who did not smoke and reported their husband smoked in close proximity to them, directly exposing them to tobacco smoke, were considered exposed to secondhand smoke; those who did not smoke and reported their husband smoked but not in close proximity to them were considered exposed to thirdhand smoke; those who reported neither they nor their husbands smoked were considered unexposed. Of the surveyed pregnant women, about 15% reported secondhand smoke exposure, and about 36% reported thirdhand smoke exposure. Less than 1% reported firsthand smoke exposure (i.e., that they were active smokers). Overall, regardless of the type of tobacco exposure (first-, second-, or thirdhand), tobacco-exposed pregnant women had lower HRQoL than unexposed women. Over half of all the tobacco-exposed pregnant women experienced health problems in all five dimensions. Furthermore, there was evidence to suggest that tobacco-exposed pregnant women experienced more limitations in their usual activity as well as worse anxiety and depression than unexposed pregnant women. Even compared to pregnant women who had physiological diseases like diabetes, pregnant women exposed to first- and secondhand tobacco smoke had comparable or lower HRQoL.
While it is encouraging that less than 1% of pregnant women reported they actively smoked, this research shows that second- and thirdhand smoke exposure harms pregnant women’s health, requiring more widespread tobacco control education efforts to prevent this exposure. As the number of smokers in China remains large, it will be harder and harder for pregnant women to protect themselves from second- and thirdhand smoke. Regulation and education are needed to add another layer of protection for this vulnerable population.

Click here to learn more about this study.

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