(NaturalNews) Women who smoke while pregnant increase the risk that their children will be born with cleft lips, according to a study conducted by researchers from the University of Bergen, Norway, and published in the journal Epidemiology.
"First trimester smoking was clearly associated with risk of cleft lip," the researchers wrote. "This effect was not modified by variants of genes related to detoxification of compounds of cigarette smoke."
The researchers found that smoking more than 10 cigarettes per day during the first trimester of pregnancy increased the risk of giving birth to a child with cleft lip by nearly 100 percent. Even nonsmokers who spent at least two hours per day in the company of smokers had a 60 percent chance of having children with cleft lips.
The researchers further conducted a genetic analysis on 1,336 infants participating in the study, including 573 with cleft lip. They recorded variations in genes associated with detoxifying cigarette smoke and compared them to occurrence of cleft lip to see if children with certain genes might be less susceptible to the effects of maternal tobacco exposure. Genetic variation had no effect, however, on the heightened risk of cleft lip associated with maternal smoking or exposure to secondhand smoke.
Cleft lip and cleft palate, two of the most common birth defects worldwide, occur when the tissues of the upper lip and the roof of the mouth, respectively, fail to fuse properly during the first trimester of pregnancy. They can lead to difficulty suckling, and poor nutrition as a consequence. In addition, the infant's unconventional appearance and difficulty speaking can interfere with socialization and emotional bonding.
Other suspected causes of cleft lip and palate include use of alcohol, drugs or anticonvulsants; exposure to lead, nitrates, organic solvents, pesticides or other pollutants; or poor nutrition by the pregnant mother.