Predicting Obstetric Vasculopathies through Study of Diastolic Notch and other Indices of Resistance to Blood Flow in Uterine Artery

Obstetric vasculopathies are a set of apparently heterogeneous and poorly understood conditions. Conditions like recurrent miscarriages due to fetal demise, pre-eclampsia, IUGR, recurrent still births and accidental hemorrhage all seem to have the same underlying etiopathology. They are grouped into one large set coined as ‘Obstetric Vasculopathies’. Resistance to blood flow in the uterine arteries can be important and effective method to predict obstetric vasculopathies (except recurrent miscarriages). Resistance to this blood flow can be measured by the presence (and subsequent disappearance) of diastolic notch as well as the standard color Doppler indices namely Pulsatility Index (PI), Resistance Index (RI) and Systolic: Diastolic (S: D) ratio. In normal pregnancy almost always at 12 to 14 weeks of duration, the uterine artery shows presence of a diastolic notch. In high-risk subjects, disappearance of diastolic notch at midtrimester in uterine artery Doppler waveform analysis if used alone may not be a good screening method for obstetric vasculopathies. However, the combination of a diastolic notch and an abnormal resistance index in both uterine arteries at 20 weeks gestation is more accurate indicator in predicting severe pregnancy complications. These subjects are almost eight times more likely to develop either: Clinically significant hypertension and/or deliver prior to 32 weeks and/or have a perinatal demise and/or have an Infant with a birth weight of less than 1500 gm. Bilateral or Unilateral: Studying bilateral uterine artery seems to be more accurate that unilateral artery for prediction of obstetric vasculopathies. Prediction in I-Trimester: Disappearance of uterine artery diastolic notch in combination with other parameters seems to be a good test for prediction of obstetric vasculopathies particularly PIH and IUGR in I-Trimester. The advantage of such an early allows an early instituting of preventive measures. Notch Depth Index (NDI): It is calculated as the depth of the diastolic notch divided by the maximal diastolic velocity. The NDI value in the second trimester is associated with the later onset of pre-eclampsia, and is clinically more useful in predicting pre-eclampsia than the two conventional indices. Abnormal maternal uterine artery Doppler in association with elevated maternal serum AFP, HCG, Inhibin A or decreased PAPP-A identifies a group of subjects at greater risk of IUGR and gestational hypertension with proteinuria. Lowdose aspirin administered as early as 14 to 16 weeks of gestation to pregnant subjects at high risk of pre-eclampsia with abnormal uterine Doppler findings may reduce or modify the course of severe pre-eclampsia and may help in prevention of IUGR.