Women exposed to second-hand smoke while pregnant are more likely to experience a stillbirth or have babies with birth defects, according to an analysis.
Stillbirth was 23pc more common and birth defects were 13pc more common among women who lived or worked with smokers, according to a report published in Pediatrics.
"Women need to be protected from passive smoke exposure before conception and throughout pregnancy," said Jo Leonardi-Bee, a professor at the University of Nottingham in England.
Although the increased risks of stillbirth and birth defects are not massive, she warned: "They are a lot larger in magnitude than one would anticipate if we believe that passive smoke only has one percent of the effect of active smoking."
Leonardi-Bee and her colleagues combined data from 19 studies that looked at the effects of secondhand smoke on the rates of miscarriage, newborn death and birth defects.