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Secondhand Smoke Exposure Adversely Affects Pregnancy Outcomes

Recently, secondhand smoking is found to be linked with pregnancy loss, including stillbirth, miscarriage and tubal ectopic pregnancy, according to a new study led by Andrew Hyland, a researcher at Roswell Park Cancer Institute (RPCI). The data of a study group of 80, 762 is provided by Women’s Health Initiative (WHI). The findings, published in the journal Tobacco Control, also reveals that the longer pregnant women are exposed to secondhand smoke, the higher risk of adverse pregnancy outcomes there will be.

It was known that smoking during pregnancy can significantly increase the risk of adverse pregnancy outcomes including spontaneous abortion or miscarriage, stillbirth and tubal ectopic pregnancy. However, there was limited evidence, before the Hyland study, to connect secondhand smoke (SHS) to adverse pregnancy outcomes. Also, it remains unclear whether there is a critical period, during which exposing to SHS leads to more adverse results.

man smoking

Smoking during pregnancy significantly increase the risk of adverse pregnancy outcomes, how about the influence of secondhand smoke? *Image source: babymed.com


The 80,762 participants in the study all passed the menopause and had at least been pregnant once. Among them, more than 5,000 (nearly 6.3 percent) are still smoking; nearly 35,000 (43 percent) were smokers and had been smoking for at least 100 cigarettes; less than 41,000 (50.6 percent) women are never-smokers.

The never-smokers were divided into different groups according to their SHS conditions. The results showed that in the 80, 762 females, 26, 307 (32.6 percent) claimed that they had been miscarried at least once; 3532 (4.4 percent) experienced stillbirth once; and 2033 (2.5 percent) had tubal ectopic pregnancy. Some key findings are:

  1. The younger and better educated females had less likelihood of having miscarriage and obstetric labor complications; compared with Caucasian American females, African and Hispanic females showed a higher likelihood of adverse pregnancy outcomes; females who have Body Mass Index (BMI) less than 26 were less likely to experience adverse pregnancy outcomes.
  2. The never-smokers, compared with participants either was still smoking or had been smoking, were less likely to have miscarriage, stillbirth and tubal ectopic pregnancy. While, there is no significant difference in adverse pregnancy outcomes between women who was smoking or had been smoking. In the never-smoker group, the probability of not having adverse pregnancy outcomes was significantly higher—the percentages of never-smokers not having miscarriage, stillbirth and tubal ectopic pregnancy were 51.5, 50.6, and 50.7 percent, respectively.
  3. Compared with never-smokers, women who smoked during pregnancy had 16 percent, 44 percent and 43 percent greater risks to have miscarriage, stillbirth and tubal ectopic pregnancy, respectively.

This correlation has also been found in never-smokers: even for those who never smoked, exposing to SHS led to greater risk of having adverse pregnancy outcomes than those who were not exposed to SHS. The longer women were exposed to SHS, the higher likelihood of adverse pregnancy outcomes it would be: in the never-smoker group, females with the highest level of SHS exposure (defined by childhood exposure for longer than 10 years, adult home exposure for more than 20 years or adult work exposure for more than 10 years) were 17 percent, 55 percent and 61 percent more likely to have miscarriage, stillbirth, and tubal ectopic pregnancy, respectively.

In addition, the study also discovered that those who only exposed to SHS in childhood had not had any kind of adverse pregnancy outcomes of miscarriage, stillbirth and tubal ectopic pregnancy. Hence, there is no such a “critical period” to be exposed to SHS and the risk of adverse pregnancy outcomes is only connected to how long females are exposed to SHS. Previous studies were not conducted in dimension of lifetime, whereas this study performed big data analysis in 40 American research center, offering a solid theoretical basis for policies such as prohibiting secondhand smoke to protect females and their offspring.

 preganant woman

Protect females and their offspring and keep them away from secondhand smoke. 

Source: EurekAlert!


  1. Andrew Hyland, et al. Associations of lifetime active and passive smoking with spontaneous abortion, stillbirth and tubal ectopic pregnancy: a cross-sectional analysis of historical data from the Women’s Health Initiative.Tob Control 2014;0:1–8. doi:10.1136/tobaccocontrol-2013-051458a