If a fetomaternal hemorrhage in excess of 30 cc has occurred, additional testing is mandatory in order to determine the appropriate dosage of RhIG to prevent alloimmunization. A positive rosette test should be followed by a quantitative test such as the Kleihauer–Betke test or an alternative approach such as flow cytometry. See the article on Kleihauer–Betke test for details on how the volume of fetomaternal hemorrhage is calculated. The dosage of RhIG is calculated from the volume of fetal hemorrhage (in mL). Ex: 50 mL fetal hemorrhage / 30 mL = 1.667 (round up to 2) then add 1 = 3 vials of RhIG.Postpartum RhIG should be administered within 72 hours of delivery. If prophylaxis is delayed, the likelihood that alloimmunization will be prevented is decreased. However, ACOG still recommends that RhIG be administered because partial protection still occurs. If the D-type of a newborn or stillborn is unknown or cannot be determined, RhIG should be administered. Immune thrombocytopenia
Primary immune thrombocytopenia (ITP) is an acquired immune-mediated disorder characterized by isolated thrombocytopenia, defined as a peripheral blood platelet count less than 100 x 109/L, and the absence of any obvious initiating and/or underlying cause of the thrombocytopenia. Symptoms of ITP include abnormal bleeding and bruising due to the reduction in platelet count. Rho(D) Immune Globulin Intravenous [Human; Anti-D] is indicated for use in non-splenectomized, Rho(D)-positive children with chronic or acute ITP, adults with chronic ITP, and children and adults with ITP secondary to HIV infection.
Following delivery
A D-negative mother who is not alloimmunized to D should also receive an appropriate dose of RhIG after delivery of a D-positive infant. After delivery, a cord blood sample from infants born to D-negative mothers should be tested for the D antigen. If the neonate is D-negative, no further RhIG is needed. However, if the infant is D-positive, the mother should have a postpartum blood sample screened for fetomaternal hemorrhage in order to determine the appropriate dosage of RhIG to be administered. (The presence of residual anti-D from antepartum RhIG administration does not indicate ongoing protection from alloimmunization- repeat administration of RhIG is necessary. )The rosette test is a sensitive method to detect fetomaternal hemorrhage of 10 cc or more. This qualitative (not quantitative) test will be positive if fetal D-positive cells are present in the maternal sample, indicating a significantly large fetomaternal hemorrhage has occurred. A rosette test may be falsely positive if the mother is positive for the weak D phenotype and falsely negative if the neonate is weak D.  If the mother is positive for the weak D phenotype, the rosette test should not be used; instead, a quantitative test such as the Kleihauer–Betke test or flow cytometry should be utilized. If the rosette test is negative, then a dose of 300 micrograms of RhIG is given (sufficient to prevent alloimmunization after delivery in 99% of cases). The RhIG dose suppresses the immune response to up to 30 cc of whole fetal blood (15 cc of red blood cells).