Abstract: Approximately 210 million pregnancies occur in world annually, which 38% of them are unplanned and 22% are aborted. About 80,000 abortion occurs each year in Iran. The main aim of this study, was determining abortion relation factors among women in Ardabil, Iran. This study is a case-control study, 200 mothers which had abortion selected randomly and 200 mothers which had delivered a term infant matched (age) with them for control group. Data were collected by interview and questionnaire and results compared together via chi square and t-test. This study showed significant relationship between abortion and history of previous abortions and pregnancies (p<0.05). Because main reason of abortion was unwanted pregnancy, contraceptive education and counseling should be considered as priorities of heath program.