Maternal cigarette smoking during pregnancy. A risk factor for childhood strabismus.

Strabismus is a common ophthalmologic disorder in children that can result in permanent visual loss. A population-based case-control study was conducted to investigate the association between childhood strabismus and prenatal risk factors including maternal smoking. All incident cases of strabismus diagnosed during a 21-month period, from January 1, 1985, to September 30, 1986, in nine metropolitan area pediatric ophthalmology centers were selected for study (n = 377). Controls were children born on the same day and in the same hospital as the cases (n = 377). Data collection included an interview with the biologic mother and abstraction of obstetric and neonatal birth records. Cigarette smoking was associated with esotropia and but not exotropia for those women who smoked throughout pregnancy (odds ratio, 1.8, 95% confidence interval, 1.1 to 2.8, and odds ratio, 1.4, 95% confidence interval, 0.6 to 3.1, respectively). The relative risk for strabismus was not elevated for women who quit smoking before pregnancy or during pregnancy, nor was there evidence of a dose response. The effect of maternal smoking on risk of esotropia was modified by birth weight and gestational age. The association of maternal smoking throughout pregnancy and esotropia was strongest for children who weighed less than 2500 g (odds ratio, 8.2, 95% confidence interval, 1.1 to 62.7) and 3500 g or more at birth (odds ratio, 5.6, 95% confidence interval, 2.1 to 15.4). Exposure to secondary smoke during pregnancy increased the risk of strabismus only when the mother smoked.