RISK-FACTORS FOR ESOTROPIA AND EXOTROPIA

Objective: To identify risk factors associated with the two major type s of strabismus-esotropia and exotropia-in a cohort of children follow ed up from gestation to age 7 years. Design: Pregnant women were enrol led in the Collaborative Project of the National Institute of Neurolog ical Disorders and Stroke, Bethesda, Md, from 1959 to 1965 at 12 unive rsity centers. This large multidisciplinary study was designed to eval uate the developmental consequences of complications during pregnancy and the perinatal period. Data on maternal, socioeconomic, perinatal, and neonatal characteristics were collected from 39 227 children and t heir mothers by medical examination and interview. Examinations of the children were performed at birth, 4 months, 8 months, 1 year, and 7 y ears. Outcome Measures: The evaluation of the presence of strabismus w as performed during follow-up examinations and confirmed at the 7-year follow-up visit. Potential risk factors for strabismus were evaluated from the maternal, socioeconomic, perinatal, and neonatal characteris tics. Results: Esotropia developed in 1187 children (3.0%), and exotro pia developed in 490 children (1.2%). Esotropia was more common in whi tes (3.9% in whites vs 2.2% in blacks, P<.0001). The occurrence of exo tropia was similar in the two races (1.2% in whites and 1.3% in blacks ). Results of multivariable logistic regression models showed that the risk of strabismus increased with low birth weight (P<.0001). For inf ants weighing 1500 g at birth compared with those weighing 4000 g at b irth, the odds ratios were 3.26 (95% confidence interval, 2.50 to 4.25 ) for esotropia and 4.01 (95% confidence interval, 2.77 to 5.80) for e xotropia. Maternal cigarette smoking during pregnancy also increased t he risk of each type of strabismus (P<.0001). For offspring of mothers who smoked more than two packs of cigarettes per day compared with th ose whose mothers did not smoke, the odds ratios were 1.83 (95% confid ence interval, 1.51 to 2.22) for esotropia and 2.32 (95% confidence in terval, 1.72 to 3.13) for exotropia. Maternal age was also a significa nt risk factor for esotropia (P=.0005). The risk of esotropia increase d with increasing age until age 34 years. In particular, the odds rati o for mothers aged 30 to 34 years relative to that for mothers aged 20 to 24 years was 1.43 (95% confidence interval, 1.19 to 1.70). Conclus ions: Esotropia was more common in whites than in blacks. The occurren ce of exotropia was similar in the two races. Maternal cigarette smoki ng during pregnancy and low birth weight were independent and importan t risk factors for both esotropia and exotropia. There was an increase d risk of esotropia with increasing maternal age.