In case you need one more reason why smoking during pregnancy is a really bad idea, a new study from Danish researchers has found that moms-to-be who smoke are much more likely to have a baby born "cross-eyed" (a medical condition known as strabismus). Published online March 25, 2010, in the American Journal of Epidemiology, the study used information from the Danish National Birth Cohort, a large scale health survey of moms and babies in Denmark. After identifying over 1,300 cases of strabismus, researchers looked at prenatal health interviews the mothers of these babies had completed—including information about smoking habits. According to researchers, women who smoked during pregnancy were at a 26 percent greater risk of having a child with strabismus compared to mothers who had not smoked.
The number of cigarettes a mom smoked seemed to matter most. Researchers noted in their report that women who smoked between five and nine cigarettes a day had a 38 percent greater risk of their baby developing strabismus compared to non-smoking mothers. Smoking 10 or more cigarettes a day was associated with a 90 percent greater risk.
"We were able to show that each extra cigarette smoked per day during pregnancy exerted a 5 percent increase in strabismus risk, which is a new finding," says lead researcher Dr. Tobias Torp-Pedersen of the Statens Serum Institute in Copenhagen, Denmark, in a Reuters Health article on the study.
Strabismus, or "cross-eyes," is the common name used to describe about 30 different muscular or nerve conditions in which the eyes are unable to line up in the same direction when focused on an image. Although strabismus affects as many as 2 to 3 percent of all children, "not much is known about its causes," reports Torp-Pedersen to Reuters Health.
According to researchers, exposure in the womb to harmful substances may be one cause of strabismus. "Nicotine and other substances in tobacco, alcohol, and caffeine all affect the brain in some way," says Torp-Pedersen. "Minor disturbances to the developing brain could plausibly lead to strabismus."
In this study, coffee and tea consumption among moms were not related to risk for strabismus.