March 13, 2011

Secondhand Smoke Exposure Increases Some Birth Risks

New research shows that expectant mothers who are exposed to secondhand smoke may have an increased risk of having a child with birth defects or who is stillborn.

The researchers, from the University of Nottingham, found that women who are passive smokers due to their proximity to someone who smoked increased their risk of stillbirth by 23 percent and of having a baby with defects by 13 percent.

They looked at data from 19 previous studies from North America, South America, Asia and Europe.

All of the studies had focused on pregnant women who did not smoke themselves but who were exposed to secondhand smoke from their partners, friends, or work colleagues who smoked.

The combined data suggests that being exposed to more than 10 cigarettes per day is enough for the risks to be increased.

However, the study did not find an increased risk of miscarriage or newborn death from passive smoking -- only an increased risk of stillbirth and birth defects. And the results didn't point to a link with any specific congenital birth defect.

The research suggests that fathers who smoke should also be more aware of the danger their smoking poses to their unborn child.

While previous research has shown that smoking by pregnant women can create serious health risks for their unborn child, Dr Jo Leonardi-Bee, lead researcher of the study and associate professor in medical statistics at the University of Nottingham, said they still did not know when the effects of secondhand smoke begin.

"What we still don't know is whether it is the effect of sidestream smoke that the woman inhales that increases these particular risks or whether it is the direct effect of mainstream smoke that the father inhales during smoking that affects sperm development, or possibly both," Leonardi-Bee told BBC News.

"More research is needed into this issue although we already know that smoking does have an impact on sperm development, so it is very important that men quit smoking before trying for a baby," Leonardi-Bee said in a press release.

"The risks are related to the amount of cigarettes that are smoked so it is therefore very important for men to cut down," she said. "Ultimately though, in the interests of their partner and their unborn child, the best option would be to give up completely."

"It is vital that women are made aware of the possible risks associated with secondhand smoke and alert those around them of the impact it could potentially have on the health of their unborn baby," Andrew Shennan, professor of obstetrics at St. Thomas' Hospital in London and spokesperson for baby charity Tommy's, told BBC.

"The chemicals in cigarettes are known to significantly increase the risk of serious pregnancy complications," said Shennan.

The study is published in the April edition of the journal Pediatrics.


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