March 7th, 2011
12:01 AM ET
Even if you don't smoke when you're pregnant, just being around smokers, can increase the risk of harming your future baby, according to a new study in the medical journal Pediatrics.
Researchers found exposure to secondhand smoke increased a non-smoking pregnant woman's chances of having a stillborn by 23 percent, and increased the risk of delivering a baby with birth defects by 13 percent.
"These results highlight the importance of smoking prevention and cessation focusing on the father in addition to the mother, during the preconception period and during the pregnancy," explains Dr. Jonathan Winickoff, Associate Professor of Pediatrics at Harvard Medical School, who is not affiliated with the study.
The team of experts reviewed virtually all available studies worldwide that focused on this health issue.
The scientists aren't exactly sure what levels of secondhand smoke are dangerous, but they do think the more exposure the higher the risks.
"We anticipate that the effect becomes significant when the woman is exposed to more than 10 cigarettes a day, which isn't a lot when you consider that some women are exposed to partners and other people's smoking habits on a daily basis. However, we need more evidence to be able to say with certainty what the true levels are," explains study author Jo Leonardi-Bee, PhD and Associate Professor in Medical Statistics at the University of Nottingham in England.
This research also suggests that secondhand smoke can be almost as dangerous to a baby as having a mother who smokes, at least when referring to stillbirths and birth defects.
Pregnant smokers have a 20 to 34% increase risk of having a baby who is stillborn compared to women who don't smoke, according to Dr. Winickoff. The risks weren't much less – 23% – for the non-smokers exposed to secondhand smoke.
The picture for birth defects is similar. The range for smoking women and birth defects is between 10 – 34%, and for pregnant women who are around smokers, 13%. Babies exposed to passive smoke were more likely to be born with major deformities of the feet, testes, or not have a brain.
"We know there are at least 400 toxic chemicals in tobacco smoke. These can get into the pregnant mother and affect her baby," says Dr. Winickoff.
Cigarettes contain heavy metals, DNA damaging agents, and class one carcinogens – the most harmful ones known.
"Protect yourself from passive smoke before and during pregnancy, not only to reduce risks of disease to yourself, but also to reduce the many harms that passive smoke can have on your future baby," says Leonardi-Bee.
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