The fetus at risk for anemia- diagnosis and management
Correction to this Consult: In Figure 2, the box that reads "Induce labor at 38-39 weeks" should read "Induce labor at 37-38 weeks". A revised Figure 2, "Algorithm for clinical management of the red cell alloimmunized pregnancy" can be found here.
- Hemoglobin value that is more than 2 SD below the mean is diagnostic of fetal anemia.
- Fetal hematocrit of less than 30% as a cutoff for fetal anemia
- Mild (MoM 0.83-0.65)
- Moderate (MoM 0.64-0.55)
- Severe (MoM < 0.55)
- Definitive diagnosis made by fetal blood sampling.
- Screening is performed with MCA Doppler.
- Delta optical density 450 to detect fetal anemia is primarily of historic interest or used when MCA not possible (not accurate for anti Kell)
EIFs are seen in 3-5% of normal fetus, with prevalence as high as 30% in fetuses of Asian mothers.
- A MCA-PSV of greater than 1.5MoM is used as a screening test to identify the severely anemic fetus
- Sensitivity of 75.5% and a specificity of 90.8% were reported for detecting severe anemia. The use of the MCA-PSV trends (as opposed to a single measurement) may decrease the false-positive rate to less than 5%.
- Start Screening typically 18-20 weeks of gestation.
- After 24 weeks of gestation, routine testing is usually done on a weekly basis
- Titers should be repeated serially every 4 weeks and then more frequently if they are found to be rising or with advancing gestational age
- Parental assessment and testing are key initial steps.
- Intrauterine Transfusion (Fresh, CMV negative irradiated and leukodepleted Type O Rh (D) negative blood) for Fetal HCT< 30%
- [Estimated fetal weight] X [EFW] (grams) X [coefficient (table)] = volume to transfuse
- The final target hematocrit should be approximately 40-50%.
Last Reaffirmed: Sep 1, 2023