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MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Antibody Screen Positive: Rh Disease and Other Atypical Antibodies
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11. Rh Disease and Other Atypical Antibodies
Step 11. Percutaneous Umbilical Blood Sampling (PUBS )
If the fetus is immature (less than 32-34 weeks), and the maternal antibody titer is rising, and the MCA studies and/or the delta OD-450 values suggest fetal anemia, fetal in utero transfusion may be indicated. This is accomplished through cordocentesis, or “PUBS” (percutaneous umbilical blood sampling
), a procedure where umbilical vein puncture is performed under ultrasound guidance.
If anemia (fetal hematocrit less than 25%) is confirmed on direct testing of fetal blood, intrauterine transfusion of already prepared washed, irradiated, type O, Rh negative (universal donor), packed red cells is then accomplished through the same puncture. Transfusion may then need to be repeated every 1-2 weeks, depending on the degree of fetal anemia and whether or not fetal hydrops is present. This is a highly technical procedure requiring considerable expertise and extensive blood bank, nursing, anesthesia, and neonatal intensivist back-up. It is also a procedure which is accompanied by a significant fetal loss rate (upwards of 1% per procedure) as a result of potential umbilical cord hematoma with cord occlusion. Both amniocentesis and cordocentesis likewise may contribute to further maternal sensitization, especially if the placenta must be traversed by the needle. Delivery, preceded by steroid administration, may be a safer option after 32-34 weeks, with neonatal transfusion as indicated.
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