ObjectiveThis study is aimed to investigate drug utilization pattern among pregnant women attending maternal and child health clinic of tertiary hospital in eastern Ethiopia from March 1 to April 20, 2018.ResultA total of 369 pregnant women medical records were reviewed. The mean age of pregnant women was 24.34 (± 4.48) years and the majority of them were within the age of 18-25 years. About three-fourths (n = 277, 75.1%) of them were urban residents. Besides, 314 (85.1%) women had taken at least one drug with a total of 377 drugs prescribed. From which, supplemental drugs accounted majority of the drug therapy (84.88%) whereas non-supplemental drugs (15.12%) were used by 41 pregnant women during the review period. According to Food and Drug Administration FDA pregnancy risk classification, 320 (84.88%) drugs were prescribed from category A; 33 (8.75%) drugs were from category B; 19 (5.04%) drugs were from category C and 5 (1.33%) drugs were from category D. There was no drug prescribed from category X. As this result indicated, there is a decrease in the prevalence of drug use from Category A to X as the possibility of potential risk to fetus might outweigh the potential benefit to the mother. Some drugs were utilized from category D for treatment of chronic illnesses.Electronic supplementary materialThe online version of this article (10.1186/s13104-018-3966-5) contains supplementary material, which is available to authorized users.