Equations used
Fetoplacental blood volume (FPV) (mL):
FPV = 1.046 + (EFW in grams × 0.14)
Volume to transfuse (mL):
Volume = FPV × (Desired Hct − Observed Hct) ÷ Donor Hct
Confirm achieved Hct/Hb with post-transfusion sampling per protocol.
Hydrops note
In fetal hydrops, EFW can be less reliable, which may affect weight-based blood-volume estimates. Some protocols use gestational-age–based blood-volume tables/estimates to reduce dependence on EFW and confirm achieved Hct/Hb by sampling.
Placental chorioangioma: increased transfusion volume may be needed
In cases of large placental chorioangioma with fetal anemia, published data suggest the blood volume required to correct anemia may be nearly twice what is normally anticipated, with wide variability. Plan for adequate blood product availability and confirm post-transfusion Hct/Hb rather than relying on a single “expected” volume.
References
- Plecas DV, Chitkara U, Berkowitz GS, et al. Intrauterine intravascular transfusion for severe erythroblastosis fetalis: how much to transfuse? Obstet Gynecol. 1990;75(6):965-969. PMID: 2342745.
- Mandelbrot L, Daffos F, Forestier F, et al. Assessment of fetal blood volume for computer-assisted management of in utero transfusion. Fetal Ther. 1988;3(1-2):60-66. doi:10.1159/000263335. PMID: 3257068.
- Hamzeh C, Green J, Hamadeh G, Korst LM, Chmait RH. Increased Intrauterine Transfusion Blood Volume Needed to Correct Fetal Anemia due to Placental Chorioangioma. Fetal Diagn Ther. 2025;52(1):90-96. PMID: 39307129;