Case-control study of nutritional and environmental factors and the risk of oral clefts in Thailand

Background One infant in 700 is born with an oral cleft. Prior studies suggest low micronutrient status is associated with an increased risk of oral clefts. Environmental factors such as passive smoke exposure or supplement use may also affect oral cleft risk. We examined nutrition and environmental related risk factors for oral clefts. Methods We conducted a case–control study in Northeast Thailand in 2012 to 2013. We enrolled 95 cases and 95 controls. We recruited cases with a nonsyndromic cleft lip with or without a cleft palate (CL±P) less than 24 months old. Cases were matched to controls on age and place of conception. We collected survey data, a food frequency questionnaire, and measured zinc concentrations in toenail trimmings. We calculated descriptive statistics by case and control status. We used conditional logistic regression to estimate unadjusted and adjusted associations, 95% confidence intervals (CIs), and p‐values. Results Any liver intake (adjusted OR [aOR] for ≥1/week versus none), 10.58; 95%CI, 1.74–64.37, overall p = 0.02) and the presence of food insecurity (aOR, 9.62; 95% CI, 1.52–61.05; p = 0.02) in the periconceptional period increased CL±P risk. Passive smoke exposure increased the risk of CL±P (aOR, 6.52; 95% CI, 1.98–21.44; p < 0.01). Toenail zinc concentrations were not associated with CL±P risk. Conclusion Our findings add to a growing body of knowledge of environmental risk factors for oral clefts from low‐ and middle‐income countries. Our findings on liver are contradictory to prior results. Large multisite studies are needed to identify environmental and genetic risk factors for oral clefts. Birth Defects Research (Part A) 106:624–632, 2016. © 2016 Wiley Periodicals, Inc.