Background
Undernutrition remains the major public health concern in Ethiopia and continues as the underlying cause of child mortality. However, there is a scarcity of information on the magnitude and determinant factors of undernutrition. Therefore, this study aimed to assess the prevalence of undernutrition and associated factors among children aged 6–59 months in East Belesa District, northwest Ethiopia.

Methods
A community-based cross-sectional study was conducted from April to May, 2014. A multistage stratified sampling technique was used to select 633 study participants. A structured interviewer-administered questionnaire was used to collect data. In order to identify factors associated with undernutrition (stunting and wasting) a multivariate logistic regression analysis was employed. The Adjusted Odds Ratio (AOR) with a 95 % Confidence Interval (CI) was computed to show the strength of the association. In the multivariate analysis, variables with a p-value of <0.05 were considered as statistically significant.

Results
In this study, about 57.7 and 16 % of the children were stunted and wasted, respectively. The odds of stunting were higher in children born to mothers who gave their first birth before 15 years of age (AOR?=?2.4; 95 % CI: 1.19, 5.09) and gave prelacteal feeding to their child (AOR?=?1.83; 95 % CI: 1.28, 2.61). However, lower odds of stunting were observed among children aged 36–47 months (AOR?=?0.41; 95 % CI: 0.22, 0.78) and had higher family monthly income, Et. Br. 750–1000, (AOR?=?0.61; 95 % CI: 0.39, 0.92). Moreover, the odds of wasting were higher among children who received butter as prelacteal food (AOR?=?2.32; 95 % CI:1.82, 5.31).

Conclusion
Child undernutrition is a critical public health problem in the study area. Advanced age of children (36–47 months) and higher family monthly income were inversely associated with stunting. However, higher odds of stunting were observed among children whose mothers delivered their first child before 15 years of age, and gave their children prelacteal feeding. Thus, delaying the first pregnancy and reducing prelacteal feeding is of a paramount significance in reducing the burden of undernutrition.