Significant advances have been made in accurate and reliable visualization of the cerebral circulation in normal and abnormal pregnancies. They provided the non-invasive studies of fetal cerebral angiogenesis and further development that filled some of the gaps made by neuroanatomical studies alone. The first breakthrough in the assessment of fetal circulation was development of Doppler system with purpose to obtain velocity waveforms. Continuing technical advances in Doppler ultrasound equipment, especially highly sensitive color flow imagining techniques have made it possible to study smaller anatomical parts of fetal circulation system including cerebral vascularization. Before examination of brain vascularity, anatomical vascular structure and development on the different appearance at each gestational age should be remembered as the basic knowledge. Since the development of the embryo is rapid and significant changes occur during even one week it is important to specify the stage of the embryo or fetus both by age (postmenstrual weeks and days) and by size (crownrump length (CRL) and biparietal diameter (BPD).

Introduction of three-dimensional (3D) sonography and 3D power Doppler techniques have enabled visualization of intracranial vessels. 3D power Doppler assessment particularly adds useful information in the prenatal evaluation of normal brain development, vascular malformation and tumoral vascularity.