Exposure to secondhand smoke may cause adverse pregnancy outcomes, according to a recent study.

Researchers from Roswell Park Cancer Institute and the University at Buffalo found that secondhand smoke could cause pregnancy loss, including miscarriage, stillbirth and tubal ectopic pregnancy. They said their findings mark a significant step toward clarifying the risks of secondhand smoke exposure.

"This study demonstrated that pregnancy outcomes can be correlated with secondhand smoking. Significantly, women who have never smoked but were exposed to secondhand smoke were at greater risk for fetal loss,"  Andrew Hyland, the study's lead investigator and Chair of RPCI's Department of Health Behavior, said in a statement.

While there have been previous studies showing the adverse effect of smoking on pregnancy outcomes, evidence showing the effects of secondhand smoke exposure on pregnancy has been limited, researchers said.

For the study, researchers collected data on more than 80,700 women

Investigators considered lifetime secondhand smoke exposure rather than only during pregnancy or reproductive years, taking into consideration smoke exposure in participants' childhood and adult years. Also, the comparison group of never-smokers was limited to women without any secondhand smoke exposure, producing a truer control group compared to previous studies.

Women with the highest levels of secondhand smoke exposure - despite never having smoked themselves - had significantly greater estimates of risk for all three adverse pregnancy outcomes, and these risks approached the risk seen among women who smoke (those who smoked more than 100 cigarettes in their lifetime). The highest levels of lifetime secondhand smoke exposure 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.

"This study offers new information for women regarding the lifetime impact secondhand smoke can have on reproductive outcomes and their ability to successfully bring a pregnancy to full term," Hyland said.

Hyland added that the strength of the study also provides public-health professionals and others with information upon which to base health guidelines about the significant consequences of secondhand smoke.