Background: Interferon beta (IFN beta) was the first proven drug for the treatment of multiple sclerosis (MS). The diagnosis of MS frequently occurs in women at child-bearing age (especially in twenties and thirties). Therefore, the pregnancy process is major concern for many women with MS. Data on women exposed to IFN beta during pregnancy are limited. The aim of our study was to investigate the teratogenic potential of IFN beta on embryonic development via embryo culture technique. Recently, this technique has been often used for determining teratogenic effect of pharmacologic drugs and potential teratogens on embryonic development.