Influence of Ethnicity on the Incidence Rate of Oral Clefts in Northern Iran

Introduction Oral clefts including cleft palate (CP), cleft lip with or without cleft palate (CL/P) and cleft lip (CL) are considered as common congenital anomalies (1). Oral clefting has reported with an incidence rate of 0.5-2.5 per 1000 live births worldwide, although ethnical and different geographical area can be the significant affect on the incidence rate (2-4) and widely among different populations (5). Previous reports have shown that the incidence rates of CL/P are varied in different region worldwide (6-8). Several factors including sex, geographic area, country, maternal nutrition and usage of the folic acid pre-pregnancy period and during the first semester of pregnancy can affect on the incidence rate of CL/P. Also, studies have shown that the role of having a child with oral clefts in the family, age, usage of alcohol, smoking, stress and tension during pregnancy, diabetes mellitus, antileptic medicine by mothers on the rate of oral clefts (9). Several complications are observed in the patients with oral clefting including poor occlusion, dental disorders, speech disorders, feeding difficulties and stigma, facial deformities and nutritional, respiratory, hearing and articulation problems (10,11). Psychological and behavioral disorders may be observed in patients with oral clefts. (12). Several studies have reported that psychiatric disorders such as depression increase in children and adolescents with oral clefts (12,13). A study has shown that male to female ratio is 2:1 and 1:2 for cleft lips and cleft palates, respectively, also unilateral and left side in cleft palates are common (14). Geographic location, socioeconomic status and racial/ ethnicity influence the incidence of oral clefts (8,13,15). Indeed, consanguineous marriages increase the incidence of congenital anomalies including CL/P (16,17). The ethnicity of the population influences the incidence rate of CL/P. It is generally thought that highest, intermediate and lowest incidence rates belong to the Asian and Native North American, Caucasian and African populations (5,18-22). Also, a study has reported that the incidence rate of CL/P is 0.5 per 1000 in Nigeria (23). According to a study in Denmark oral clefts are more in babies born to women which were originally from Denmark compared to those born to foreign women (24). In Iranian population, the rate of oral clefts determined to be 0.86-3.73 per 1000 births (25). Also, the rate of CL/P is reported 0.97 per 1000 live births in northern Iran during 1998-2003 (26).