Fetal cerebrovascular circulation: a review of prenatal ultrasound assessment

Antenatal intrauterine cerebrovascular events were found to play an important role in the pathogenesis of perinatal brain damage. Changes in placental vascular resistance, cardiac contractibility, vessel compliance, and blood viscosity alter the normal dynamics of fetal cerebral circulation. The circulatory mechanisms described in animal fetuses also operate in the human fetus. The isthmus of the aorta represents a watershed area reflecting the redistribution of blood during increased peripheral resistance and hypoxia. The fetal cerebrovascular system acts locally within the skull and interacts with the other components of fetal circulation to compensate by redistribution of blood in case of shortage in resources. The introduction of various sonographic techniques and the collection of data from the arterial and venous cerebral circulation have improved our understanding of the regulatory mechanisms involved in fetal cerebral hemodynamic events. Anatomical and physiological considerations of cerebral vasculature in health and disease are relevant in the research of variations in fetal brain blood perfusion. Changes in flow characteristics in fetal cerebral vasculature can be used for clinical decisions. However, caution is advised before applying research data into practice. The clinical utility is well established in situations of fetal compromise such as growth restriction and anemia.