Maternal cigarette smoking and oral clefts: A meta-analysis

Objective: A meta-analysis was performed to estimate the association between maternal cigarette smoking and the risk of having a child with a nonsyndromic oral cleft (NSOC). Design: Studies published from 1966 through 1996 were retrieved using MEDLINE, Current Contents, bibliographies, and other sources. MEDLINE and Current Contents search terms included 'oral clefts,' 'cigarette smoking,' 'birth defects,' and 'congenital malformations.' Cohort and case-control studies that enrolled oral cleft patients [cleft lip with or without cleft palate (CL/P), cleft palate (CP), or both] and controls, and presented information on maternal cigarette exposure during pregnancy were included in the analysis. Descriptive and outcome data from each study were independently abstracted by two authors. Results: The overall odds ratio of the 11 studies satisfying criteria was 1.29 [95% confidence interval (Cl), 1.18 to 1.42] for CL/P and 1.32 (95% CI: 1.10 to 1.62) for CP, indicating a small increased risk of having a child with either a CL/P or a CP for mothers who smoke during the first trimester of the pregnancy. Conclusions: These analyses suggest a small but statistically significant association between maternal cigarette smoking during the first trimester of gestation and increased risk of having a child with a CL/P or CP.