Researchers studied the effects of smoking and infant transforming growth factor alpha (TGFA) alleles in an ethnically homogenous setting to determine their possible association with nonsyndrome cleft lip and/or palate (CLP). Medical histories and interview information were obtained for mothers of 302 CLP cases and for 567 mothers of non-malformed children. Multivariate logistic regression analyses revealed that smoking was associated with cleft lip and/or cleft palate (odds ratio = 1.40, 95% confidence interval 0.99 – 2.00), whereas TGFA was not associated with CLP. Identify: a. Study Design. b. Exposure. c. Outcome. d. Advantage.