P94Fetal cerebrovascular response to chronic hypoxia

Abstract

ObjectiveTo study the cerebral and umbilical hemodynamics changes in hypoxic and growth‐retarded fetuses. To determine if at long‐term, fetal brain hyperperfusion with loss of cerebral vascular flow velocity variability is associated with brain damage and poor fetal outcome.MethodsThe fetal blood flow redistribution was assessed by using Doppler cerebral‐umbilical ratio in 8 growth‐retarded fetuses, mainly every day. The evolution of the fetal hemodynamics was interpreted according to the clinical, anatomical and histological data.ResultsAll 8 fetuses had poor fetal outcome including fetal death (n = 5). Fetal blood flow redistribution with brain hyperperfusion was detected in all fetuses during the whole period of observation. The early phase of fetal deterioration was characterized by the development of oligohydramnios and the disappearance of the cerebral flow velocity variability. During the later phase of deterioration, fetal heart rate decelerations and the increase of cerebral vascular resistance with reduction of brain perfusion were detected. Histological study of the brains showed hypoxic lesions.ConclusionThe loss of variability of the cerebral resistance index, in the cases of absent umbilical end diastolic flow, and the loss of variability of the cerebral‐umbilical ratio in the other cases, identifies the beginning of the period of very high risk for the fetus. Such a pattern may be considered as a predictor of brain lesion and poor fetal outcome. These results also indicate the existence of two phases in the fetal cerebrovascular response to chronic hypoxia.