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Maternal smoking, passive smoking boost risk of neural tube defects

Smoking cigarettes causes more than lung cancer.  A new study in the Nov 15, 2010 issue of Birth Defects Research. Part A, Clinical and Molecular Teratology suggests that passive smoking during pregnancy can boost risk of having a baby with neural tube defects or NTDs.

Both passive smoking and active smoking have been known to boost death risk from heart disease, stroke, infections, asthma, and lung cancer among other things in smokers and passive smokers.

World Health Organization researchers have recently reported passive smoking or secondhand smoke kills about 600,000 people worldwide each year, including 379,000 deaths from heart disease, 165,000 deaths from lower respiratory infections, 36,900 deaths from asthma and 21,400 lung cancer deaths.

The current study led by Suarez L and colleagues from Texas Department of State Health Services in Austin, Texas found mothers exposed only to passive smoking were 70 percent more likely to have a baby with neural tube defects that nonsmokers and those who were not exposed to passive smoking.

According to the authors, cigarette smoke is known to harm developing embryos although evidence for an independent effect on the risk of neural tube defects is mixed.

For the study, Suarez et al. analysed data from a total of 1041 cases of neural tube defects and 5862 live births as controls delivered during 1997 to 2004 to see if smoking and passive smoking is linked to risk of the birth defects.

The researchers did find an positive association between exposure to passive smoking and risk of the birth defects, after adjustment for race-ethnicity, and study center.

The association was also found by other researchers.

For instance, Li ZW and colleagues from Peking University in  Beijing China also conducted a case and control study in 2008 and found women with occasional passive smoking were 51 percent more likely to have children with NTDs and those with passive smoking for almost everyday during the peri-conceptional period were 144 percent more likely to have NTDs in off spring, compared to women without passive smoking.

Their findings were reported in  Zhonghua liuxingbingxue zazhi (Chinese Journal of Epidemiological Research).

It is interesting that the researchers of the current study did not find an increase in the risk in those who were actively smoking 24 or fewer cigarettes a day although those who actively smoked 25 or more per day were found 60 percent more likely to have a baby with neural tube defects.

But the association disappeared after adjustments for confounders.

The researchers concluded "Results suggest that maternal exposure to passive smoke is associated with NTDs. Women who plan on becoming pregnant should minimize their exposure to passive smoke and refrain from smoking."

A health observer suggests that all women who plan to have a baby should avoid both active and passive smoking prior to or after becoming pregnant as tobacco smoke has been known to be a risk for many health conditions, regardless of what the researchers of the current study found.

Jimmy Downs