Background: Adverse pregnancy outcomes lead to serious health consequences to the mother and/or the baby. These Adverse birth outcomes; prematurity, low birth weight and still birth represent significant problems in both developing and developed countries. Adverse pregnancy outcomes are still major public health problems in developing countries including Ethiopia where most pregnancies are unplanned, complications are many and outcomes are generally Unfavorable for both mother and infant.Objective: To identify determinants of adverse pregnancy outcomes among deliveries takes place in Jimma University specialized hospital from January1 -December 31 / 2015. Methods:The study was a facility based unmatched casecontrol study design conducted by reviewing mothers and newborn cards and registration log book who delivered in Jimma university specialized hospital from January 1 / 2015 to December 31/2015, southwest Ethiopia. The study was done on randomly selected 86 cases and 258 controls using structured data collection checklist. Data analysis was done by SPSS version 20 and multiple logistic regression statistical methods were used to identify the predictors. Result:In this study 344 mothers and newborns cards were included yielding 100% response rate. From this 86 mothers and newborn cards were selected for case group and 258 mothers and newborn cards were selected for control group. Most of the cases 80.2% and controls 82.9% were between the age group of 20-34 years. Mothers who are referred for delivery service from other area are more than five times to have adverse pregnancy outcomes than mothers who are not referred, AOR=5.49 95% CI [2.80-10.76]. And mothers who had illness during