Maternal smoking and orofacial clefts.

To investigate a possible association between maternal smoking during pregnancy and oral clefts, a study was conducted using Swedish health registries. Infants with oral clefts (N = 1834) were selected among 1,002,742 infants born between 1983 and 1992 with known smoking exposure in early pregnancy. Confounders such as maternal age and parity were controlled for by using the Mantel-Haenszel technique. A statistically significant association with maternal smoking was found. The odds ratio (OR) for any maternal smoking among cases of cleft lip with or without cleft palate [CL(P)] was 1.16 (95%Cl: 1.02-1.32). For cases of cleft palate alone (CP), the corresponding OR was 1.29 (95%Cl: 1.08-1.54). The results of the present study, based on the largest series of oral cleft cases published to date, indicate that cigarette smoking during pregnancy is associated with increased risks of CL(P) and CP.