Spontaneous abortion (SA) is one of the most prevalent negative reproductive outcomes among women around the world. It occurs naturally without any human intervention and complicates about 15–20% pregnancies globally. A cross sectional study was conducted to determine prevalence of spontaneous abortion and associated factor among pregnant women visiting inAddis-alem Primary and Felege-Hiwot Comprehensive Specialized Referral Hospitals, Bahir Dar, Ethiopia. Socio demographic, life style, and obstetric related data were collected through semi-structured questionnaires from 403 randomly selected mothers at maternity wards of the two hospitals. Anthropometeric and hemoglobin level measurements of these women were also recorded. The data were entered into and analyzed using SPSS Version 20. Chi-square test, binary and multivariate logistic regression analysis were used to evaluate the possible associations and assess the effect of important explanatory variables with miscarriage. Statistical significance was determined at p < 0.05 and P value less than 0.25 in bivariate logistic regression analyses were used to select variables for analyzes in multivariate logistic regression model. The prevalence of spontaneous abortion in this study was 91/403 (22.58%). Women age above 40 years old was 5.41 times more likely to have spontaneous abortion as compared to younger age groups. Miscarriage was 66 % less likely to occur in rural among women residing in rural setting. The likelihood of miscarriage was 11.38, 10.92 and 5.46 times higher among occupationally daily laborer, house wives and privately employed women, respectively. Women who earn lower monthly income of 1000-2999 ETB were 4.88 times more likely to encounter spontaneous abortion than high monthly income >5000 ETB. Spontaneous abortion was 10.39-fold higher among pregnant women who had previous history of abortion as compared to without previous history of abortion. Underweight and overweight pregnant women were at 5.01 and 10.91 times increased as compared to women with normal body weight. The odds of spontaneous abortion were 2.80 times more among women with mild anemia as compared with non-anemic women. The risk of spontaneous abortion was 7.39-folds higher women who had exposure to cigarette smoke at home compared with not passive smokers. Women with diabetic condition were at greater (13.36-fold higher) risk of spontaneous abortion as compared with non-diabetic women. This study concluded that there was no association between spontaneous abortion and any of the socio-demographic characteristics, educational status, alcohol consumption, drug use, thyroid problem and hypertension.Creating awareness among community, particularly the women about the risk factors of spontaneous abortion for making strong generalization are recommended