Obstetric ultrasound imaging requires the acquisition of a standard set of maternal and fetal images. Our objective was to evaluate the impact of implementation of a protocol-based ultrasound examination on the duration of ultrasound examinations, examination completion, and accuracy of documentation.We conducted a case-cohort study. Obstetric ultrasound examinations performed in the first, second, and third trimesters were reviewed before and after implementation of a protocol-based ultrasound examination. The duration of the ultrasound examination, number of missing required images, and documentation of missing images were abstracted from an image archival system. To account for clustering by sonographer, 3 mixed effects models with a fixed effect for protocol and a random intercept for sonographer were used to evaluate the effect on the total time of the examination, number of missing images, and whether missing images were documented.A total of 100 ultrasound examinations were compared: 50 before and 50 after implementation of the protocol. Statistically significant differences between outcomes before and after protocol implementation were observed for all outcomes. After implementation of the protocol, the average duration of ultrasound examinations decreased by 7.62 minutes (95% confidence interval [CI], 3.57-11.68 minutes); the number of missing images was reduced by 5.81 per examination (95% CI, 4.24-7.39); and proper documentation of missing images increased by 40.24% (95% CI, 22.77%-57.71%).Implementation of a software protocol-based ultrasound examination significantly improved the efficiency and accuracy of obstetric ultrasound examinations in this study.