Studies of role of smoking in TGF-A and MSx1 genes as covariates have suggested that the risk for orofacial clefting may be influenced by maternal smoking alone as well as combination with the presence of uncommon TGF-A allele.[18] With respect to lack of association between maternal smoking and risk for orofacial cleft in this study in contrast to other studies [4][5][17][20][22][23][24] the current data support the possibility that smoking has a different effect on cleft risk among women which may reflect a role for genetic susceptibility factors in cleft development. Here, MSX1 is linked to orofacial cleft.