Monitoring for Fetal Anemia

An Rh-positive fetus in a sensitized mother should be monitored for fetal anemia. Serial amniocentesis for evaluation of bilirubin (the Delta OD₄₅₀) can be used to quantify fetal hemolysis.

Ultrasound can also be used by measuring the the peak systolic velocity (PSV) of the middle cerebral artery (MCA). Serial measures of MCA PSV are plotted as a function of gestational age and compared to control values.

Mari et al (2000) plotted the PSV of the MCA of fetuses with no anemia or mild anemia (open circles), moderate or severe anemia (triangles), and those with hydrops (solid circles). They found that fetuses with moderate or severe anemia had PSVs values greater than 1.50 times the median (dotted curve).

References

Mari G et al. Non-invasive diagnosis by Doppler ultrasonography of fetal anemia due to maternal red-cell alloimmunization. N Engl J Med 2000;342:9–14.