For the emergency physician tasked with evaluating the patient with an obstetric emergency, ultrasound can provide important and potentially life-saving information. Ultrasound of the pregnant patient is unique in that two possible approaches can be used: transabdominal and transvaginal. Another unique feature is that an understanding of developmental anatomy, which changes during pregnancy, is important. Two of the most basic yet important uses of ultrasound in the pregnant patient are to provide information concerning the gestational age of the pregnancy and the fetal heart rate. Ultrasound has a major role in the diagnosis and management of the patient with a suspected ectopic pregnancy.