Pulsed-wave Doppler ultrasound is a widely used technique for monitoring pregnancies. As ultrasound equipment becomes more advanced, it becomes harder to train practitioners to be proficient in the procedure as it requires the presence of an expert, access to high-tech equipment as well as several volunteering patients. Immersive environments such as mixed reality can help trainees in this regard due to their capabilities to simulate real environments and objects. In this article, we propose a mixed reality application to facilitate training in performing pulsed-wave Doppler ultrasound when acquiring a spectrogram to measure blood velocity in the umbilical cord. The application simulates Doppler spectrograms while the trainee has the possibility of adjusting parameters such as pulse repetition frequency, sampling depth, and beam-to-flow angle. This is done using a combination of an optimized user interface, 3D-printed objects tracked using image recognition and data acquisition from a gyroscope. The application was developed for Microsoft HoloLens as the archetype of mixed reality, while a 3D-printed abdomen was used to simulate a patient. The application aims to aid in both simulated and real-life ultrasound procedures. Expert feedback and user-testing results were collected to validate the purpose and use of the designed application. Design science research was followed to propose the intended application while contributing to the literature on leveraging immersive environments for medical training and practice. Based on the results of the study, it was concluded that mixed reality can be efficiently used in ultrasound training.