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Smoking is implicated in congenital birth defects

Dominika Osmolska Psy.D.'s picture

We all know smoking is ill-advised during pregnancy, but most of us have a fairly vague idea of the reasons why. Quick – can you name some of the potential risks to the baby if a pregnant mother smokes? Though low birth weight and premature birth have long been associated with smoking, you may be surprised at some of the other, serious risk factors uncovered in a new study.

The European study, out of the University College London, looked at data over a 50-year-period and fleshes out in remarkable detail some of the more alarming side effects of smoking during pregnancy.

For starters, smoking is associated with an increased rate of cleft lip and palate, a congenital abnormality usually associated with low folate (vitamin B9) levels in the mother. It turns out that smoking contributes to the development of the deformity regardless of other factors. Oral facial abnormalities can arise when a flat embryo becomes a tube in the third week of pregnancy. It's a precarious time for an embryo, and smoking can disturb the process.

Congenital heart disease is also associated with smoking while pregnant. It is a type of defect or malformation in one or more structures of the heart or blood vessels that occurs before birth. Typical congenital heart defects include heart valve defects, defects in the walls separating the atria or ventricles, or heart muscle abnormalities. Many of these defects can be corrected surgically, though such surgeries are costly, necessitate long stays in the hospital and may not fully correct the problem.

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The London study looked at nearly 174,000 cases of malformations, compared with close to 12 million control cases, to conclude that cigarette chemicals including nicotine, carbon monoxide and tar can lead to limb deformities, clubfoot and gastrointestinal and optical disorders.

The study also validated that smoking during pregnancy can lead to stillbirth, technically defined as a baby dying in utero more than halfway through the pregnancy. Premature birth, also a risk factor for smoking moms, is associated with multiple medical complications for babies, including respiratory distress, developmental disability, cerebral palsy, hemorrhage, and infection, among others.

Even secondhand smoke is hazardous: earlier this year, a study by University of Nottingham researchers found that the risk of stillbirth jumped 23% when pregnant non-smokers breathed in smoke at home or at the office.

Smoking also affects fertility adversely, making it more difficult to conceive in the first place. Shockingly, there is also some evidence that smoking may predispose infants to future behavioral challenges and criminal propensities. According to that study, adults whose mothers were heavy smokers during pregnancy were 30% more likely to have been arrested than those whose mothers were light or nonsmokers. Further, they were more likely to be repeat offenders.

Worldwide, 250 million women use tobacco daily, according to statistics from the 14th World Conference on Tobacco or Health held in 2009 in Mumbai.

The review was published Monday in the journal Human Reproduction Update.