Maternal
Cigarette Smoking During Pregnancy
A Risk Factor for Childhood Strabismus Rosemarie B.
Hakim, PhD, James
M.
Tielsch,
Strabismus is a common ophthalmologic disorder in children that can result in permanent visual loss. A population\x=req-\ 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). \s=b\
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.
(Arch Ophthalmol. 1992;110:1459-1462) Accepted for publication March 25, 1992. From the Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, The Johns Hopkins University Schools of Medicine and Public Health, Baltimore, Md. Presented in part at the 23rd Annual Meeting of the Society for Epidemiological Research, Snowbird, Utah, June 14, 1990. Reprint requests to The Johns Hopkins Hospital, 600 N Wolfe St, Wilmer Room 120, Baltimore, MD 21205 (Dr Tielsch).
PhD
Strabismus costly requires therapy
is a common disorder in children that intensive and surgery. Strabis¬ mus is thought to be a defect in cen¬ tral nervous system control over the oculomotor system and is the most common cause of amblyopia, a major cause of vision loss in the United States.13 The etiology of nonrestrictive stra¬ bismus is not well understood but is presumably related to factors affecting the normal development of the oculo¬ motor control mechanism. Because this system is not fully matured at birth and requires significant postnatal external stimuli to develop properly,1 strabismus has not usually been regarded as a con¬ genital anomaly or birth defect. Thus, little work has been done to examine epidemiologie risk factors for adverse pregnancy outcomes and their associa¬ tion with risk of strabismus. Among the many risk factors for adverse outcomes of pregnancy, maternal cigarette smok¬ ing during pregnancy is one that has been studied widely and associated with a variety of such events, including in¬ trauterine growth retardation, prema¬ ture birth, miscarriage, and certain congenital anomalies.413 Because of
smoking's wide range of effects, we hy¬ pothesized that it could play a role in the development of this abnormality. Herein, we present results from a population-based study of maternal smoking and risk of strabismus among their offspring. SUBJECTS AND METHODS
metropolitan area. Deviations less than 9 PD were excluded because they are not readily
diagnosed and thus would not be represen¬ tative of the full spectrum of microdeviations. The children with strabismus were under the age of 7 years at the time of diag¬ nosis, and all were born in Baltimore area hospitals. Subjects with nonconcomitant (re¬ strictive or paralytic) strabismus, usually caused by congenital extraocular tendon re¬ striction, and those who had Down syndrome were excluded from the study. To select controls, the next three infants born after each case were chosen from the delivery log at the case's hospital of birth. If the first control identified could not be lo¬ cated, the next sequential live birth was se¬ lected. There was one control per case. To preclude contamination of the control group with cases, mothers were asked if their child had strabismus, amblyopia, or any related eye problem before being interviewed. If a positive response was obtained, that control was made ineligible and the next live birth was selected. A total of 427 eligible cases were ascer¬ tained from the nine ophthalmic clinics and practices. Of these, 14 mothers (3.3%) re¬ fused to participate, 22 mothers (5.2%) could not be located after extensive tracing efforts, and six cases (1.4%) had biologic mothers that were unavailable because of mother's death, adoption of child, language barriers, or illness. Controls could not be found for an additional two cases, leaving a total of 383 cases (90.1%). All apparent cases of concom¬ itant strabismus were accepted for initial screening. Subsequently, the ophthalmic records of all cases were reviewed by an ex¬ pert in strabismus who reclassified them into exotropia or one the several subtypes of es¬ otropia. Six cases that could not be catego¬ rized or had other rare forms of strabismus were excluded from this analysis, leaving 377 cases.
Cases were children first diagnosed with concomitant (nonrestrictive and nonparalytic) strabismus between January 1, 1985, and September 30, 1986, at nine Baltimore, Md, area strabismus clinics and pediatrie ophthalmology practices. Based on a survey conducted in 1984 of pediatrie ophthalmology referral patterns in the Baltimore area (un¬ published), it was estimated that these nine sources saw approximately 75% to 80% of all newly diagnosed cases of strabismus with deviations of at least 9 prism diopters in the
Four hundred eighty-five controls were identified from birth logs, 13 (2.7%) of whom had strabismus or a related eye problem and were therefore excluded, leaving 472 eligible controls. Of the remaining eligible controls, 18 (3.8%) had missing records, 16 (3.4%) had mothers who refused to participate, 54 (11.4%) could not be located, and one (0.2%) had a mother who could not be interviewed because of deafness. The six controls matched to the unclassified cases of strabismus were also ex¬ cluded. Controls were slightly more difficult
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Table 1.—Distribution of Strabismus Cases by Age at Onset Reported by Parent and by Age at Diagnosis
Table 2.—Association of Maternal
Smoking Esotropia
Maternal
Age,
Age at Diagnosis, No. (%)_No. (%) 1 (0.3) 109(32.0) 81 (23.8) 83(22.0) 97(28.4) 146(38.7) 47(13.7) 105(27.9) 7(2.1) 42(11.1)
Reported Age at Onset, mo
Cigarette Smoking During Pregnancy
A Risk Factor for Childhood Strabismus Rosemarie B.
Hakim, PhD, James
M.
Tielsch,
Strabismus is a common ophthalmologic disorder in children that can result in permanent visual loss. A population\x=req-\ 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). \s=b\
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.
(Arch Ophthalmol. 1992;110:1459-1462) Accepted for publication March 25, 1992. From the Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, The Johns Hopkins University Schools of Medicine and Public Health, Baltimore, Md. Presented in part at the 23rd Annual Meeting of the Society for Epidemiological Research, Snowbird, Utah, June 14, 1990. Reprint requests to The Johns Hopkins Hospital, 600 N Wolfe St, Wilmer Room 120, Baltimore, MD 21205 (Dr Tielsch).
PhD
Strabismus costly requires therapy
is a common disorder in children that intensive and surgery. Strabis¬ mus is thought to be a defect in cen¬ tral nervous system control over the oculomotor system and is the most common cause of amblyopia, a major cause of vision loss in the United States.13 The etiology of nonrestrictive stra¬ bismus is not well understood but is presumably related to factors affecting the normal development of the oculo¬ motor control mechanism. Because this system is not fully matured at birth and requires significant postnatal external stimuli to develop properly,1 strabismus has not usually been regarded as a con¬ genital anomaly or birth defect. Thus, little work has been done to examine epidemiologie risk factors for adverse pregnancy outcomes and their associa¬ tion with risk of strabismus. Among the many risk factors for adverse outcomes of pregnancy, maternal cigarette smok¬ ing during pregnancy is one that has been studied widely and associated with a variety of such events, including in¬ trauterine growth retardation, prema¬ ture birth, miscarriage, and certain congenital anomalies.413 Because of
smoking's wide range of effects, we hy¬ pothesized that it could play a role in the development of this abnormality. Herein, we present results from a population-based study of maternal smoking and risk of strabismus among their offspring. SUBJECTS AND METHODS
metropolitan area. Deviations less than 9 PD were excluded because they are not readily
diagnosed and thus would not be represen¬ tative of the full spectrum of microdeviations. The children with strabismus were under the age of 7 years at the time of diag¬ nosis, and all were born in Baltimore area hospitals. Subjects with nonconcomitant (re¬ strictive or paralytic) strabismus, usually caused by congenital extraocular tendon re¬ striction, and those who had Down syndrome were excluded from the study. To select controls, the next three infants born after each case were chosen from the delivery log at the case's hospital of birth. If the first control identified could not be lo¬ cated, the next sequential live birth was se¬ lected. There was one control per case. To preclude contamination of the control group with cases, mothers were asked if their child had strabismus, amblyopia, or any related eye problem before being interviewed. If a positive response was obtained, that control was made ineligible and the next live birth was selected. A total of 427 eligible cases were ascer¬ tained from the nine ophthalmic clinics and practices. Of these, 14 mothers (3.3%) re¬ fused to participate, 22 mothers (5.2%) could not be located after extensive tracing efforts, and six cases (1.4%) had biologic mothers that were unavailable because of mother's death, adoption of child, language barriers, or illness. Controls could not be found for an additional two cases, leaving a total of 383 cases (90.1%). All apparent cases of concom¬ itant strabismus were accepted for initial screening. Subsequently, the ophthalmic records of all cases were reviewed by an ex¬ pert in strabismus who reclassified them into exotropia or one the several subtypes of es¬ otropia. Six cases that could not be catego¬ rized or had other rare forms of strabismus were excluded from this analysis, leaving 377 cases.
Cases were children first diagnosed with concomitant (nonrestrictive and nonparalytic) strabismus between January 1, 1985, and September 30, 1986, at nine Baltimore, Md, area strabismus clinics and pediatrie ophthalmology practices. Based on a survey conducted in 1984 of pediatrie ophthalmology referral patterns in the Baltimore area (un¬ published), it was estimated that these nine sources saw approximately 75% to 80% of all newly diagnosed cases of strabismus with deviations of at least 9 prism diopters in the
Four hundred eighty-five controls were identified from birth logs, 13 (2.7%) of whom had strabismus or a related eye problem and were therefore excluded, leaving 472 eligible controls. Of the remaining eligible controls, 18 (3.8%) had missing records, 16 (3.4%) had mothers who refused to participate, 54 (11.4%) could not be located, and one (0.2%) had a mother who could not be interviewed because of deafness. The six controls matched to the unclassified cases of strabismus were also ex¬ cluded. Controls were slightly more difficult
Downloaded From: http://archopht.jamanetwork.com/ by a Karolinska Institutet University Library User on 05/25/2015
Table 1.—Distribution of Strabismus Cases by Age at Onset Reported by Parent and by Age at Diagnosis
Table 2.—Association of Maternal
Smoking Esotropia
Maternal
Age,
Age at Diagnosis, No. (%)_No. (%) 1 (0.3) 109(32.0) 81 (23.8) 83(22.0) 97(28.4) 146(38.7) 47(13.7) 105(27.9) 7(2.1) 42(11.1)
Reported Age at Onset, mo
