Ultrasound Monitoring of Fetuses With Vascular Intra-uterine Growth Restriction (IUGR) Using the Isthmus Systolic Index (ISI): Feasibility, Comparison to Normal Fetuses and Association With Perinatal Mortality

Today evaluating the hemodynamic tolerance of the fetus with IUGR, is based on clinical evidence of fetal well-being and ultrasound arguments, since we know in fact that there is a correlation between Doppler indices of cardiovascular function and perinatal mortality.

The flow to the systolic aortic isthmus may be a marker of systolic performance balance of both ventricles. An index of systolic flow velocities (ISI) has previously been described in a population of normal fetuses. Fetuses with IUGR, the velocities recorded in the aortic isthmus could be affected and the normal development of the ISI should be changed, because of the increase in placental resistance on one hand, and the gradual deterioration ventricular functions on the other one. Investigators hypothesize that the ISI index in the context of placental insufficiency could provide additional arguments on the extraction timing, the prognosis and the fetal extraction mode to severe hypoxia.

The strategy evaluates the feasibility of measuring the ISI index on Doppler systolic flow in the aortic isthmus in the follow-up by ultrasound of the fetus with IUGR due to placental insufficiency.

The ISI is obtained from this flow by calculating the ratio of the minimum systolic velocity (called Nadir) on the peak systolic velocity (called Peak) or Nadir / Peak. The fetal extraction decision (birth) will be taken, blinded the outcome of the ISI, following the protocol of national recommendations for the management of fetuses with IUGR.