Fetal growth restriction secondary to placental insufficiency remains a major cause of perinatal morbidity and mortality. Decision for a preterm delivery must take into account on the one hand of complications related to prematurity, and on the other hand of risk of cerebral damage due to fetal hypoxia.
In this section, statements underlying the clinical importance of recording fetal aortic isthmus flow during placental circulatory insufficiency are outlined. Apprehending the bases of fetal circulation dynamics, you will understand the influence of both placental and cerebral vascular impedances over the diastolic flow through the fetal aortic isthmus. Thus, an increase in placental vascular resistance associated with cerebral vasodilatation can cause a reversal of diastolic flow through the isthmus leading to perfusion of the brain with red cells poorly saturated in oxygen.