Secondhand smoke increases risk of pregnancy loss

According to a new study in Tobacco Control, women exposed to secondhand smoking (SHS), particularly those with no history of smoking, have a higher risk of spontaneous abortions, ectopic pregnancies, and stillbirths than women with no such exposure.

Investigators at the Roswell Park Cancer Institute and the University of Buffalo performed a cross-sectional analysis on the historical reproductive data of 80,762 women who had participated in the Women’s Health Initiative Observational Study. Self-reported lifetime active and passive tobacco smoke exposure, self-reported spontaneous abortions, stillbirths, and ectopic pregnancies were assessed.

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In comparison with women with no history of active smoking, women who had any period of active smoking during their reproductive years had an odds ratio (OR) 1.16 (95% confidence interval [CI] 1.08 to 1.26) for 1 or more spontaneous abortions; 1.44 OR (95% CI 1.20 to 1.73) for 1 or more stillbirths; and 1.43 OR (95% CI 1.10 to 1.86) for 1 or more ectopic pregnancies. Women who never smoked, but had the highest levels of lifetime SHS exposure (childhood >10 years, adult home >20 years, and adult work >10 years) had an adjusted OR (aOR) of 1.17 (95% CI 1.05 to 1.30) for spontaneous abortion, 1.55 (95% CI 1.21 to 1.97) for stillbirth, and 1.61 (95% CI 1.16 to 2.24) for ectopic exposure, when compared to women with no smoking history and no SHS exposure. 

The researchers concluded that exposure to SHS increased the risk of adverse pregnancy outcomes. In women with the highest amount of SHS exposure, the risk of adverse pregnancy outcomes approached the risk of women who had a history of smoking more than 100 cigarettes in their lifetime.

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