Variability in Middle Cerebral Artery Doppler Measurements in Uncomplicated Term Pregnancies.

Measuring the resistance in the fetal middle cerebral artery (MCA) is an important factor in assessing fetal well-being. On its own, the Pulsatility Index (PI) in the MCA may indicate a decrease in fetal oxygenation. Furthermore, the PI measured in the Fetal MCA is an index parameter in the calculation of the Cerebro-Placental Ratio (CPR) used to evaluate whether there is an existing disturbance in the Placental-Umbilical and Feto-cerebral circulations. The CPR is a measurement that enables practitioners to predict the fetuses reaction to intrauterine hypoxemia. The CPR measurement is commonly used to evaluate small for gestational age (SGA) fetuses and to distinguish between constitutionally small fetuses and ones that suffer from placental insufficiency. For those who suffer from placental insufficiency, the CPR measurement is an aid in deciding the optimal time and mode of delivery.

Recently, researchers pondered if the CPR measurement may aid in predicting disturbance in fetal oxygenation during delivery. A number of studies have showed that appropriate for gestational age fetuses with abnormal CPR measurements may be susceptible to delivery complications in the same manner as fetuses who suffer from placental insufficiency. The question that is yet to be answered is whether the MCA measurement reliable in term pregnancies. This question arises due to the impression that the MCA measurement at term is highly variable, even when taken under optimal conditions.

The aim of this study is to evaluate the intra-observer variability in the MCA measurement under optimal conditions, in Uncomplicated Term Pregnancies.