Citation, DOI, disclosures and article data
Citation:
Venkatesh M, Skandhan A, Knipe H, et al. Fetal MCA systolic/diastolic ratio. Reference article, Radiopaedia.org (Accessed on 19 Mar 2024) https://doi.org/10.53347/rID-25519
Fetal MCA systolic/diastolic (S/D) ratio is an important parameter in fetal middle cerebral arterial Doppler assessment. It is a useful predictor of fetal distress and intrauterine growth restriction (IUGR).
Interpretation
Normal
During pregnancy the middle cerebral (and other intracranial) arteries demonstrate high resistance waveforms, i.e. high systolic velocity and low/absent diastolic velocity.
The normal value of fetal MCA S/D ratio will vary by institution. A normal fetal MCA S/D ratio should always be higher than the umbilical arterial S/D ratio. The fetal MCA S/D ratio value will decrease as the pregnancy progresses.
Abnormal
A reduced S/D ratio is abnormal and implies an increased diastolic flow in MCA. Loss of high resistance waveform is also an indicator of fetal distress or IUGR.
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1. Fong KW, Ohlsson A, Hannah ME et-al. Prediction of perinatal outcome in fetuses suspected to have intrauterine growth restriction: Doppler US study of fetal cerebral, renal, and umbilical arteries. Radiology. 1999;213 (3): 681-9. Radiology (full text) - Pubmed citation
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2. Meyberg R, Ertan AK, Tossounidis I et-al. Reference ranges and standard percentile-curves for the Doppler indices RI and S/D ratio of the fetal middle cerebral artery. Color Doppler measurements in a perinatal centre. Clin Exp Obstet Gynecol. 2001;27 (2): 106-8. Pubmed citation
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