Most patients in the United States have an indication for and receive sonography during pregnancy. The issue of routine sonography for low-risk women continues to be contentious even though the randomized trials have not been able to demonstrate a clear benefit. Clinics that routinely offer sonography for all pregnancies usually schedule such a procedure at 16 to 20 weeks of gestation. Although great progress is being made in the first-trimester diagnoses of congenital anomalies, most targeted studies are performed at 18 to 20 weeks of gestation. Although many private obstetricians perform in-office sonography, the highest rates of detection of congenital anomalies are seen in tertiary care settings such as a university medical center. In difficult or otherwise high-risk cases, a consulting perinatologist is commonly the physician most likely to integrate the ultrasound findings with a rational management plan for the remainder of the pregnancy and for delivery.