ABSTRACT
If the hematocrit is below the fifth percentile (0.84 MOM) for GA, blood is transfused in a sterile fashion. A computer program (e.g., https://www.perinatology.com/protocols/rhc. htm) can be used to estimate the amount of blood to transfuse based on the initial fetal hematocrit, the estimated fetal weight and the concentration of the blood transfused (43,44). The following formula is used:
Vtransfused ðmLÞ ¼ Vfetoplacental ðmLÞðHctfinal HctinitalÞ
A final fetal blood sample is taken a few seconds after the transfusion has been completed. If the fetus is hydropic, it is better to perform more than one transfusion at a distance of three to five days to increase the hematocrit to the median hematocrit value for GA. At and after 24 weeks, the fetal heart rate should be monitored for the next two to three hours until fetal movements resume. The risk of fetal death is 1% to 2% even with ultrasound guidance, expert operators, and accurate management.
