Fetal Cerebral Blood Flow (Dys)autoregulation.

: As an extremely sensitive organ, particularly during in utero development, the brain has intrinsic systems to reduce the risk of cerebral damage in cases of insult, such as energy deprivation, due to a mechanism of positive balance in cerebral oxygen-energy substrate demand and supply. This mechanism is called cerebral autoregulation and is present in both the fetal and adult brain. The inaccessibility of the fetal brain to currently available measurement techniques limits its knowledge. Physiological and pathological alterations of fetal cerebral blood flow (CBF) can be assessed during the latter half of pregnancy using sonographic Doppler studies. The limited studies on this subject suggest a potential role for Doppler assessment of the fetal internal carotid artery. : This article reviews the concept of CBF autoregulation and the role of fetal Doppler studies in various brain vascular territories in clinical practice. : A PubMed search was performed, and 156 English articles were used as references in this bibliographic review, published between January 1996 and December 2021. : The study of fetal CBF involves indirect observation; the fetal brain constantly changes its characteristics towards complete maturation, which will be fully accomplished only after birth, and the maternal environment influences this process. : Doppler study of the internal cerebral artery might be useful in clinical practice. However, technical issues for its study are not established, there are no reference curves, and studies on its clinical value have limited applicability.