The International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) has published guidelines on the use of Doppler ultrasound of the fetoplacental circulation at 11–13+6 weeks. When performing Doppler imaging, the displayed thermal index (TI) should be less than equal to 1.0 and exposure time, usually no longer than 5–10 minutes and not exceeding 60 minutes. The aim is to describe pulsed Doppler ultrasound and its different modalities such as spectral Doppler, color flow mapping, and power Doppler, which are commonly used to study the maternal–fetal circulation.