Ultrasonography of the normal fetal brain

Since the early 1960s it has been possible to identify the fetal head using A-mode ultrasound. The introduction of high-resolution, real-time, grayscale ultrasound in the mid-to-late 1970s first enabled the routine display of subtle internal anatomy. Using presently available equipment, the fetus can be imaged from 7 weeks after the last menstrual period until term and the internal anatomy of the fetal head can be detected after 11–12 weeks. The ultrasonic anatomy of the normal fetal head throughout the second and third trimesters is discussed, as are the normal changes taking place with growth.