Abstract: Objective To analyze the effects of environmental factors in the first trimester of pregnancy on development of nonsyndromic cleft lip with or without cleft palate(nsCL/P).Methods Totally 212 patients of nsCL/P and 221 controls with trauma or bone fracture were selected from the Affiliated Hospital of Guiyang Medical College and Baise Peopleπs Hospital.Aface-to-face questionnaire interview to parents of the subjects was conducted.The environmental risk factors were analyzed with unconditional univa riate and multivariate logistic regression models.Results The ratios of the casesπfathers and mothers with middle school education(37.7% and 27.4%)were lower compared with that of the controlsπ (60.6% and 57.0%).The ratios of the casesπfathers and mothers being peasants(77.4% and 77.8%)were higher than that of the control group(52.5% and 52.5%).After adjusting for education level and occupation of father and mother,the results of multivariate analysis showed that maternal passive smoking(OR=1.643),infection(OR=2.741)in the first trimester of pregnancy,paternal alcohol drinking(OR=1.793)before realizing pregnancy were significan trisk factors of nsCL/P.Conclusion It is important for gestation couple to avoid smoking,alcohol drinking and infection to prevent nsCL/P.