Preliminary study of environmental risk and protective factors during pregnancy for cleft lip with or without palate in the Korean population

Objective: To investigate which types of environmental exposure during pregnancy are risk and protective factors for cleft lip with or without cleft palate (CL/P). Methods: This case-control study included 278 orthodontic patients with CL/P (CL/P group) and 51 without CL/P (non-CL/P group). Demographic and environmental exposure data were collected using questionnaires completed by the parents. Statistical analyses were performed to identify the potential risk and protective factors for CL/P. Results: The two groups did not show significant difference in (1) body weight at birth and number of previous births; (2) fathers' ages at birth and occupation; (3) parents' chronic diseases, alcohol consumption, and exposure to harmful substances; and (4) mothers' smoking, secondhand smoking, and vitamin and calcium intake. Most patients with CL/P were born at normal term (≥ 37 weeks, 93.2%) with normal body weight (2.9-3.7 kg, 63.7%) and as either the first or second child (90.3%). In the CL/P group, the percentages of mothers who were very young or old (≤ 19 years, ≥ 40 years) and with physical labor in their occupation were low (1.8% and 2.2%, respectively). Compared with the non-CL/P group, the CL/P group showed a lower percentage of maternal folic acid intake (68.6% vs. 20.9%, odds ratio [OR] = 0.121; P < 0.001) and higher percentages of mothers' drug intake and fathers' smoking habits (3.9% vs. 16.2%, OR = 4.73, P < 0.05; 39.2% vs. 61.2%, OR = 2.44, P < 0.01). Conclusions: The findings of this study may explain the association between environmental factors and CL/P risk.