↑ middle cerebral artery (MCA) peak systolic velocity (PSV) suggests diagnosis of fetal anemia

High-output heart failure is late finding

• ○
  

  Cardiomegaly, polyhydramnios

  
  
• ○
  

  Hydrops

  
  
  
  
  • –
    

    Pericardial &/or pleural effusion, ascites, anasarca

  
  

Rhesus or other RBC antigen incompatibility

• ○
  

  Antibodies cross placenta → fetal RBC lysis → anemia

  
  
• ○
  

  Subsequent pregnancies with similar or more severe hemolysis

Other causes of fetal anemia

• ○
  

  Infection: Parvovirus most common

  
  
• ○
  

  Fetal hemorrhage from any cause

  
  
• ○
  

  Twin anemia-polycythemia sequence

  
  
  
  
  • –
    

    From fetofetal transfusion in monochorionic twins

  
  
  
  
• ○
  

  α-thalassemia

Monitor anemia risk with serial MCA PSV measurements

• ○
  

  Follow multiples of median (MoM) values

Fetal intervention based on risk for significant anemia

• ○
  

  ↑ risk of anemia if MCA PSV is ≥ 1.50 MoM

  
  
• ○
  

  ↑ false-positive rates when > 35-week gestational age

Ultrasound guidance used to access fetal circulation and give RBC transfusion

• ○
  

  Cordocentesis: Umbilical vein (UV) blood sampled and sent to lab for fetal hematocrit value

  
  
• ○
  

  Intrauterine transfusion: RBCs given to fetus via UV

MCA waveform acquisition tips

• ○
  

  Doppler gate placed near origin of MCA

  
  
• ○
  

  Angle of insonation should be 0°

Obtain several MCA PSV measurements

• ○
  

  Choose best measurement with best technique, not average of MCA PSVs