For each cigarette a pregnant woman lights up each day, she raises her baby's risk of squint by 5 percent.
For each cigarette a pregnant woman lights up each day, she raises her baby's risk of strabismus (squint) by 5 percent. Further, the effect of smoking on the debilitating eye disorder may become more potent later in pregnancy.
Although strabismus is a common condition, affecting some 2 to 3 percent of children, not much is known about its causes. Strabismus, often called "cross-eyes", is a collective term for about 30 different conditions in which the eyes are unable to line-up in the same direction when focusing on an image. Some subtypes are linked with muscle problems, while others are linked to nerve damage. Left uncorrected, strabismus may lead to irreversible vision loss, in addition to psychological and social consequences.
Exposure in the womb to harmful substances may be one cause of strabismus. Previous research had linked smoking and alcohol consumption during pregnancy to strabismus. But most of these studies were small and did not thoroughly investigate the timing and quantity of the exposures. To investigate this, researchers identified more than 1,321 cases of strabismus from the Danish National Birth Cohort. All of the children were born between 1996 and 2003. Their mothers were interviewed twice during pregnancy, as well as at 6 and 18 months after delivery.
It was found that women who smoked during pregnancy were at a 25 percent higher risk of having a child with strabismus compared to mothers who had not smoked, after adjusting for other risk factors such as alcohol consumption and the mother's age. The effect was not significant for smoking limited to the first trimester, but increased to 45 and 35 percent, respectively, for those who smoked during the first two or all three trimesters.
It was also noted that women smoking between five and nine cigarettes a day had a 40 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. The effects were nearly the same between strabismus subtypes and no added risk was seen with light smoking (less than five cigarettes a day), nicotine replacement therapy, or coffee or tea consumption.
Although strabismus is a common condition, affecting some 2 to 3 percent of children, not much is known about its causes. Strabismus, often called "cross-eyes", is a collective term for about 30 different conditions in which the eyes are unable to line-up in the same direction when focusing on an image. Some subtypes are linked with muscle problems, while others are linked to nerve damage. Left uncorrected, strabismus may lead to irreversible vision loss, in addition to psychological and social consequences.
Exposure in the womb to harmful substances may be one cause of strabismus. Previous research had linked smoking and alcohol consumption during pregnancy to strabismus. But most of these studies were small and did not thoroughly investigate the timing and quantity of the exposures. To investigate this, researchers identified more than 1,321 cases of strabismus from the Danish National Birth Cohort. All of the children were born between 1996 and 2003. Their mothers were interviewed twice during pregnancy, as well as at 6 and 18 months after delivery.
It was found that women who smoked during pregnancy were at a 25 percent higher risk of having a child with strabismus compared to mothers who had not smoked, after adjusting for other risk factors such as alcohol consumption and the mother's age. The effect was not significant for smoking limited to the first trimester, but increased to 45 and 35 percent, respectively, for those who smoked during the first two or all three trimesters.
It was also noted that women smoking between five and nine cigarettes a day had a 40 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. The effects were nearly the same between strabismus subtypes and no added risk was seen with light smoking (less than five cigarettes a day), nicotine replacement therapy, or coffee or tea consumption.
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