Doppler studies of fetal cerebral blood flow

Doppler flow velocity waveforms from fetal cerebral vessels can be reliably obtained by a transabdominal or transvaginal scanning route. Changes in pulsatility imply alterations in cerebral impedance and reflect the physiological regulatory mechanisms underlying pathological processes during pregnancy. In fetuses severely distressed due to failure of placental function, the ratios reflecting the redistribution of fetal circulation (e.g. the 'brain-sparing effect') help to identify fetuses at risk for fetal hypoxia. Apart from providing an increase in medical knowledge, this non-invasive technique is proving to be clinically useful.