Fetal middle cerebral arterial Doppler assessment
Fetal middle cerebral arterial (MCA) Doppler assessment is an important part of assessing fetal cardiovascular distress, fetal anaemia or fetal hypoxia. In the appropriate situation it is a very useful adjunct to umbilical artery Doppler assessment. It is also used in the additional work up of
- intra-uterine growth restriction (IUGR)
- twin to twin transfusion syndrome (TTTS) 5
- twin anaemia polycythaemia sequence (TAPS)
For an accurate measurement, the fetal head should be in the transverse plane. The MCA vessels are often found with colour or power Doppler ultrasound overlying the anterior wing of the sphenoid bone near the base of the skull. An angle of insonation of < 15o should be used; typically, an angle that approximates zero degrees can be achieved by moving the transducer on the maternal abdomen.
Parameters used include
- fetal MCA time averaged mean velocity (TAMV)
- fetal MCA pulsatility index (PI)
- fetal MCA peak systolic velocity (PSV): the highest velocity should be recorded
- fetal MCA systolic/diastolic (S/D) ratio: a normal fetal MCA S:D ratio should always be higher than the umbilical arterial S:D ratio.
- cerebroplacental ratio (CPR): ratio of pulsatility index of MCA and umbilical artery
- in the normal situation the fetal MCA has a high resistance flow which means there is minimal antegrade flow in fetal diastole.
- in pathological states this can turn into a low resistance flow mainly as a result of the fetal head sparing theory.
- paradoxically in some situations such as with severe cerebral oedema, the flow can revert back to a high resistance pattern when the pathology hasn't yet resolved.
- cerebroplacental ratio > 1:1 is normal , <1:1 is abnormal
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- 10 . Bano S, Chaudhary V, Pande S et-al. Color doppler evaluation of cerebral-umbilical pulsatility ratio and its usefulness in the diagnosis of intrauterine growth retardation and prediction of adverse perinatal outcome. Indian J Radiol Imaging. 2010;20 (1): 20-5. doi:10.4103/0971-3026.59747 - Free text at pubmed - Pubmed citation
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Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Fetal middle cerebral arterial (mca) Doppler||✗|
|Fetal MCA Doppler assessment||✗|
|Fetal middle cerebral arterial (MCA) Doppler ultrasound assessment||✗|
|Fetal middle cerebral arterial (MCA) Doppler assessment||✗|