Tehran University of Medical Sciences Journal of Biostatistics and Epidemiology 2383-4196 7 4 2021 12 15 392 402 Melkamu Zeru Department of Statistics, College of Sciences, Bahir Dar University, Bahir Dar, Ethiopia 2021 07 09 2021 08 21 Introduction: Unplanned pregnancy is a public health problem that affects maternal and child health, including maternal death, abortion, and low birth weight. Consequently, the government established family planning for action to prevent and reduce the health problems for most disadvantaged women. Objective: This study was to investigate the determinant factors of unplanned pregnancy among pregnant women in Ethiopia. Methods: A Population based cross-sectional study was conducted from Ethiopian 2016 demographic healthsurvey data. A total of 3894 pregnant womenwereincludedinthestudyandthesampleswereselectedtroughmultistagestratifiedclustersampling.Uni-variate and multiple logistic regression analysis was used toidentify factors associated with an unplanned pregnancy. Variables with p-value < 0.05 were identified assignificantfactors. Result: Among 3894 study pregnant, 31.05% of pregnancies was unplanned. The analysis result revealed that women whose age ≤ 30 years [AOR = 5.42, 95 % CI=2.38 - 12.34], women in rural [AOR=1.11, 95% CI=1.03 - 2.39], illiterate women [AOR=2.3,95% CI=2.02 - 4.09], women drinks alcohol [AOR=1.45,95% CI=1.31- 1.67], smoker women [AOR= 1.52, 95% CI 1.49 - 2.65 ],women chewing chat[AOR=1.66, 95% CI=1.66 1.18 - 2.33], unemployed women[AOR = 4.97, 95%CI=1.31-12.38] , poor economic level [AOR=8.42,95%CI=5.87- 14.39] and none-user contraceptive methods [AOR=1.7, 95% CI=1.14 – 3.87] were found to be associated with unplanned pregnancy(p < 0.05). Conclusion: The prevalence of unplanned pregnancy in the study area was 32.05%. The findings suggest that certain groups of women are at increased risk of unplanned pregnancy and would benefit from targeted family planning interventions https://jbe.tums.ac.ir/index.php/jbe/article/view/627