I-46: Obstetrical Doppler

Accurate assessment of gestational age, fetal growth, and the detection of fetal and placental abnormalities are major benefits of sonography. Color Doppler can be used to assist in the identification of vascular architecture, detection of vascular pathology and visualization of blood flow changes associated with physiologic processes and disease states. The clinical applications of obstetrical Doppler are Intrauterine Growth Restriction, diagnosis of fetal anemia and twin-twin transfusion syndrome. The use of Doppler during antenatal fetal surveillance has involved assessment of (1) the umbilical arterial and venous flow velocity waveforms, (2) the fetal cerebral circulation, and (3) the fetal venous circulation, in particular the ductus venosus. Doppler studies of the fetal circulation in intrauterine growth retardation and hypoxia have demonstrated increased resistance to flow in the umbilical arteries and redistribution in the fetal circulation with reduced resistance and increased velocity in the internal carotid and middle cerebral artery and the opposite in the descending thoracic aorta. Assessment of placental function using umbilical artery Doppler velocimetry: Placental insufficiency can be quantified based on the reduction of end-diastolic Doppler flow velocity into (1) reduced enddiastolic flow velocity, (2) absent end-diastolic flow velocity, and (3) reversed end-diastolic flow velocity. Use of middle cerebral artery velocimetry to detect fetal hypoxia: an increase in pCO2 or a reduction in pO2 will cause an increase in fetal cerebral arterial Doppler end-diastolic flow velocity, likely related to cerebral vasodilatation. This phenomenon has been described as the “brain sparing” effect. Use of Doppler to detect fetal anemia: The MCA-PSV is an accurate predictor of severe fetal anemia in pregnancies complicated by red cell alloimmunization. Use of uterine artery Doppler to detect maternal complications of pregnancy: The uterine artery Doppler reflects fetal response to stress of hostile intrauterine environment (pregnancy-induced hypertension, re-eclamptic toxemia). Fetal venous flow: The umbilical vein, ductus venosus and the inferior vena cava are the main areas of interest in the investigation of venous blood return to the fetal heart. Pulsatile umbilical vein flow and back flow in ductus venosus and IVC are indications advanced cardiac decompensation.