Among women who reported never having smoked, those exposed to secondhand smoke were more likely to have had fetal loss—spontaneous abortion (miscarriage), stillbirth, or tubal ectopic pregnancy—compared with women who had not smoked who had not been exposed to secondhand smoke. Those were the findings of a cross-sectional analysis of historical data from the Women's Health Initiative (WHI) study now available online ahead of print in the journal Tobacco Control (doi:10.1136/tobaccocontrol-2013-051458).
“The takeaway message is that secondhand smoke exposure can harm unborn babies. We often think that harm caused by smoking or secondhand smoke happens to older people, but this study reframes that paradigm,” the study's lead author, Andrew Hyland, PhD, Chair of the Department of Health Behavior at Roswell Park Cancer Institute, said via email.
The study analyzed pregnancy outcomes for 77,805 women who participated in the WHI Observational Study who reported being pregnant at least once—comparing those who reported having ever smoked themselves with those who reported never having smoked, as well as comparing the outcomes of the women based on their smoking status and self-reported level of secondhand smoke exposure.
Secondhand smoke exposure levels were defined by childhood exposure for longer than 10 years, adult home exposure for more than 20 years, and adult work exposure for more than 10 years.
Key findings were that:
- Compared with women who had never smoked (defined in the study as not having smoked more than 100 cigarettes in their lifetime) and were not exposed to secondhand smoke, women who were smokers had higher rates of spontaneous abortion;
- Women who reported never having smoked who were exposed to any secondhand smoke throughout their lifetime were more likely to have one or more spontaneous abortions than women who reported never smoking who were not exposed to secondhand smoke; and
- Women with higher levels of secondhand smoke exposure were more likely to have had spontaneous abortion, tubal ectopic pregnancies, and stillbirths than those with lower levels of secondhand smoke exposure.
The size and strength of the study provides reliable information on which to base health guidelines relating to secondhand smoke and its consequences, Hyland added. “The public health message is clear—that exposure to secondhand smoke can harm unborn babies,” he said. “It's important that this message gets out so that more smoke-free spaces are provided to protect public health.”