"Obtain a true axial view of the fetal head including thalami and sphenoid wings."
"Use colour or power Doppler to identify the MCA over the anterior sphenoid wing."
"Sample close to the MCA origin at the carotid siphon; more peripheral sampling underestimates PSV."
"Maintain an angle of insonation"
"Use a 2‑mm sample gate."
"Record during fetal quiescence (no breathing or movement), as accelerations can falsely elevate PSV late in gestation."
"Take ≥3 waveforms and use the highest PSV."
"Used for non‑invasive detection of fetal anaemia; PSV > 1.5 MoM predicts moderate–severe anaemia with high accuracy."
"Ratio of MCA PI / umbilical artery PI."
"The MCA normally demonstrates high‑resistance flow with low diastolic velocities."
"In hypoxaemia or placental insufficiency, the MCA becomes low‑resistance with increased diastolic flow, reflecting cerebral vasodilation."
"This correlates with fetal hypoxaemia and adverse outcomes in FGR."
"CPR >1.0 is normal; CPR"
"May occur transiently due to probe compression and is not necessarily pathological."
"MCA‑PSV > 1.5 MoM → high risk of moderate–severe anaemia."
"MCA‑PSV should replace ΔOD450; amniocentesis is no longer recommended for diagnosis."
"If MCA‑PSV is elevated or the fetus is hydropic → fetal blood sampling and readiness for intrauterine transfusion (IUT)."
"MCA‑PSV can guide timing of the second IUT, but is less reliable for the third transfusion."
"MCA PI and CPR are strong predictors of adverse perinatal outcomes, including NICU admission and intrapartum compromise."
"CPR is now widely incorporated into term FGR surveillance."
"MCA‑PSV is essential in diagnosing TAPS, where discordant MCA‑PSV values identify anaemic vs polycythaemic twins."
"Post‑laser TTTS surveillance includes MCA‑PSV to detect delayed anaemia."
"MCA‑PSV can be reliably measured from 16–18 weeks."
"After 35 weeks, false‑positive rates for anaemia increase; however, normal values remain reassuring."
"Updated gestational age‑specific centile charts (2025)17 are available for improved accuracy."
"Used for non‑invasive detection of fetal anaemia; PSV > 1.5 MoM predicts moderate–severe anaemia with high accuracy."
"MCA‑PSV > 1.5 MoM → high risk of moderate–severe anaemia."
"Used for non‑invasive detection of fetal anaemia; PSV > 1.5 MoM predicts moderate–severe anaemia with high accuracy."
"The Society for Maternal–Fetal Medicine (SMFM)15 recommends MCA‑PSV as the primary technique for detecting fetal anaemia. Key points:"
"MCA‑PSV > 1.5 MoM → high risk of moderate–severe anaemia."
"MCA‑PSV can be reliably measured from 16–18 weeks."
"intra-uterine growth restriction (IUGR) otherwise known as Fetal Growth Restriction (FGR)"
"Obtain a true axial view of the fetal head including thalami and sphenoid wings."
"Use colour or power Doppler to identify the MCA over the anterior sphenoid wing."
"Sample close to the MCA origin at the carotid siphon; more peripheral sampling underestimates PSV."
"Maintain an angle of insonation"
"Use a 2‑mm sample gate."
"Record during fetal quiescence (no breathing or movement), as accelerations can falsely elevate PSV late in gestation."
"Take ≥3 waveforms and use the highest PSV."
"Used for non‑invasive detection of fetal anaemia; PSV > 1.5 MoM predicts moderate–severe anaemia with high accuracy."
"Ratio of MCA PI / umbilical artery PI."
"Widely used in FGR to assess redistribution"
"The MCA normally demonstrates high‑resistance flow with low diastolic velocities."
"This correlates with fetal hypoxaemia and adverse outcomes in FGR."
"Reversal back to high resistance despite ongoing pathology (e.g., severe cerebral oedema) is a poor prognostic sign.2,3"
"May occur transiently due to probe compression and is not necessarily pathological."
"Post‑laser TTTS surveillance includes MCA‑PSV to detect delayed anaemia."
"After 35 weeks, false‑positive rates for anaemia increase; however, normal values remain reassuring."
"Updated gestational age‑specific centile charts (2025)17 are available for improved accuracy."
"Obtain a true axial view of the fetal head including thalami and sphenoid wings."
"Obtain a true axial view of the fetal head including thalami and sphenoid wings."
"Obtain a true axial view of the fetal head including thalami and sphenoid wings."
"Use colour or power Doppler to identify the MCA over the anterior sphenoid wing."
"Sample close to the MCA origin at the carotid siphon; more peripheral sampling underestimates PSV."
"Sample close to the MCA origin at the carotid siphon; more peripheral sampling underestimates PSV."
"Maintain an angle of insonation"
"Maintain an angle of insonation"
"Use a 2‑mm sample gate."
"Record during fetal quiescence (no breathing or movement), as accelerations can falsely elevate PSV late in gestation."
"Take ≥3 waveforms and use the highest PSV."
"Take ≥3 waveforms and use the highest PSV."
"Used for non‑invasive detection of fetal anaemia; PSV > 1.5 MoM predicts moderate–severe anaemia with high accuracy."
"Used for non‑invasive detection of fetal anaemia; PSV > 1.5 MoM predicts moderate–severe anaemia with high accuracy."
"Ratio of MCA PI / umbilical artery PI."
"Normal physiology"
"The MCA normally demonstrates high‑resistance flow with low diastolic velocities."
"The MCA normally demonstrates high‑resistance flow with low diastolic velocities."
"Brain‑sparing / redistribution"
"In hypoxaemia or placental insufficiency, the MCA becomes low‑resistance with increased diastolic flow, reflecting cerebral vasodilation."
"In hypoxaemia or placental insufficiency, the MCA becomes low‑resistance with increased diastolic flow, reflecting cerebral vasodilation."
"In hypoxaemia or placental insufficiency, the MCA becomes low‑resistance with increased diastolic flow, reflecting cerebral vasodilation."
"Severe pathology"
"Reversal back to high resistance despite ongoing pathology (e.g., severe cerebral oedema) is a poor prognostic sign.2,3"
"Cerebroplacental ratio (CPR)"
"CPR >1.0 is normal; CPR"
"End‑diastolic flow reversal"
"May occur transiently due to probe compression and is not necessarily pathological."
"1. Fetal anaemia"
"The Society for Maternal–Fetal Medicine (SMFM)15 recommends MCA‑PSV as the primary technique for detecting fetal anaemia. Key points:"
"The Society for Maternal–Fetal Medicine (SMFM)15 recommends MCA‑PSV as the primary technique for detecting fetal anaemia. Key points:"
"MCA‑PSV > 1.5 MoM → high risk of moderate–severe anaemia."
"MCA‑PSV > 1.5 MoM → high risk of moderate–severe anaemia."
"MCA‑PSV should replace ΔOD450; amniocentesis is no longer recommended for diagnosis."
"If MCA‑PSV is elevated or the fetus is hydropic → fetal blood sampling and readiness for intrauterine transfusion (IUT)."
"MCA‑PSV can guide timing of the second IUT, but is less reliable for the third transfusion."
"MCA‑PSV can guide timing of the second IUT, but is less reliable for the third transfusion."
"2. Growth restriction (FGR)"
"MCA PI and CPR are strong predictors of adverse perinatal outcomes, including NICU admission and intrapartum compromise."
"CPR is now widely incorporated into term FGR surveillance."
"3. TTTS and TAPS"
"MCA‑PSV is essential in diagnosing TAPS, where discordant MCA‑PSV values identify anaemic vs polycythaemic twins."
"Gestational age considerations"
"MCA‑PSV can be reliably measured from 16–18 weeks."
"After 35 weeks, false‑positive rates for anaemia increase; however, normal values remain reassuring."
"After 35 weeks, false‑positive rates for anaemia increase; however, normal values remain reassuring."
"Updated gestational age‑specific centile charts (2025)17 are available for improved accuracy."
"Sample close to the MCA origin at the carotid siphon; more peripheral sampling underestimates PSV."
"CPR >1.0 is normal; CPR"
"The Society for Maternal–Fetal Medicine (SMFM)15 recommends MCA‑PSV as the primary technique for detecting fetal anaemia. Key points:"
"MCA PI and CPR are strong predictors of adverse perinatal outcomes, including NICU admission and intrapartum compromise."
"Clinical Applications"
Expected headings
"Doppler ultrasound technique"
"Interpretation"
"Clinical Applications"
"Sample close to the MCA origin at the carotid siphon; more peripheral sampling underestimates PSV."
"Used for non‑invasive detection of fetal anaemia; PSV > 1.5 MoM predicts moderate–severe anaemia with high accuracy."
"CPR >1.0 is normal; CPR"
"MCA‑PSV should replace ΔOD450; amniocentesis is no longer recommended for diagnosis."
"After 35 weeks, false‑positive rates for anaemia increase; however, normal values remain reassuring."