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Consanguineous marriage is strongly favored in many large human populations. In the most parts of south Asia, consanguineous marriage account for 20%  to over 50% of the general population. The effect of consanguinity on hereditary deafness has been well studied and documented. Many authors have suggested that approximately one half  of sensory neural hearing loss in children can be attributed to hereditary causes. This research was carried out in Rehabilitation Deputy of welfare organization of Iran in seven provinces. 1352 infants and preschool aged children participate in this research. The prevalence of SNHL due to consanguineous  marriage in first cousin and second cousin were studied. Consanguinity was found among 45.7% in first cousin and 17.2% in second cousin. Hereditary Factors were thought  to be the cause of 863(62.9%) of bilateral SNHL children in this research. The incidence of hereditary hearing impairment is very high in developing countries  compared to developed countries. Prevention is essential to reduce the incidence of genetic hearing loss. Consanguinity should be discouraged and genetic counseling is to be applied at least for those at risk of developing genetic diseases including hearing impairments.