The "definition" of the 20-week scan should now be significantly expanded. Traditionally, the objectives of such an examination were the determination of gestational age, the detection of congenital morphologic defects, and the cursory evaluation of placental location and amniotic fluid volume. Remarkable progress has been made in intervening years. Great technical strides have been accomplished in sonographic resolution. Along with proper training of personnel improved diagnostic accuracy for anomaly detection can be anticipated. It is likely that the more recent applications of ultrasound such as uterine artery Doppler velocimetry and cervical status evaluation could equal or eclipse the significance and clinical benefits of anomaly detection.