Читать книгу Protocols for High-Risk Pregnancies - Группа авторов - Страница 69

In Rh disease, a fetal RBC antigen enters the maternal bloodstream and stimulates antibody production against that RBC antigen. An amnestic response may occur in a subsequent pregnancy if the same RBC antigen is presented to the mother’s immune system and this may lead to a series of events that include fetal anemia, extramedullary hematopoiesis, hydrops fetalis, and fetal death. Historically, the degree of fetal anemia and need for fetal RBC transfusion involved an amniocentesis to determine the amniotic fluid ΔOD450 to assess the degree of RBC‐derived hemoglobin breakdown products and to estimate anemia. Isoimmunization with the Kell antibody also results in fetal anemia but does so through bone marrow suppression rather than hemolysis and thus, the ΔOD450 will not be abnormal. Fetal anemia can also result from infections such as parvovirus B19. Doppler velocimetry of the middle cerebral artery (MCA) is now used to determine the risk for moderate to severe anemia supplanting the previously used amniocentesis. If moderate to severe anemia is suspected, the fetus should undergo a fetal blood sampling and transfusion.