Maternal smoking during pregnancy and the risk of strabismus in offspring: a meta-analysis

The effect of maternal smoking during pregnancy on strabismus in offspring remains unclear. We conducted a meta-analysis to summarize epidemiological evidences on the association between maternal smoking during pregnancy and the risk of offspring strabismus. Eligible studies were searched from the PubMed, Ovid, Embase and CNKI databases up to May 2018. The qualities of included articles were assessed with the Newcastle-Ottawa Scale and the assessment scale recommended by the Agency for Healthcare Research and Quality. Odds ratios (ORs) corresponding with its 95% confidence intervals (CIs) were pooled to estimate the effects of maternal cigarette smoking on the risk of offspring strabismus. Subgroup analyses and meta-regression were performed to explore the potential sources of heterogeneity. The Begg's test and Egger's test were used to assess the publication bias. Eleven articles involving 4,833 patients with strabismus were included. The pooled OR showed that maternal smoking during pregnancy was significantly associated with strabismus in offspring (OR = 1.46, 95% CI = 1.32-1.60). Compared with less than 10 cigarettes per day (OR = 1.17, 95% CI = 1.06-1.29), maternal smoking 10 cigarettes or more per day during pregnancy significantly increased the risk of offspring strabismus (OR = 1.79, 95% CI = 1.39-2.31). The risk of developing esotropia and exotropia for smoking pregnant women, respectively, increased by 65% (OR = 1.65, 95% CI = 1.31-2.09 and OR = 1.65, 95% CI = 1.24-2.19) than those who did not smoke during pregnancy. Additionally, the increased risk of maternity smoking associated with offspring strabismus was stable across all subgroup analyses. Overall, maternal smoking during pregnancy was associated with a significantly increased risk of offspring strabismus and the result was persistent in subgroup analyses, suggesting the importance in changing smoking habit or smoking cessation for women who are pregnant or preparing to.