Rh Incompatibility was found in 5-Minute Clinical Consult which helps you diagnose, treat, and follow up on over 900 medical conditions seen in everyday practice.
Explore 5-Minute Clinical Consult - view these FREE monographs:
-- The first section of this topic is shown below --
- Antibody-mediated destruction of red blood cells (RBCs) that bear Rh surface antigens in individuals who lack the antigens and have become isoimmunized (sensitized) to them
- System(s) affected: Hematologic/Lymphatic/Immunologic
- Synonym(s): Rh isoimmunization; Rh alloimmunization; Rh sensitization
Predominant age and sex: Affects fetuses/neonates of isoimmunized child-bearing females
- Of white population, 15% and smaller fractions of other races are Rh-negative and susceptible to sensitization (1).
- Any Rh-positive pregnancy in an Rh-negative woman can result in sensitization.
- Native risk of isoimmunization after Rh-positive pregnancy had been estimated at ≤15%, but seems to be decreasing.
- The risk of isoimmunization antepartum is only 1–2%.
- The risk of isoimmunization is 1–2% after spontaneous abortion and 4–5% after induced abortion (2).
- Use of Rho(D) immunoglobulin prophylaxis has reduced incidence of isoimmunization to <1% of susceptible pregnancies.
- Complex autosomal inheritance of polypeptide Rh antigens; 3 genetic loci with closely related genes carry an assortment of alleles: Dd, Cc, and Ee (3).
- Individuals who express the D antigen (also called Rho or Rho[D]) or its weak D (Du) variant are considered Rh-positive. Individuals lacking the D antigen are Rh-negative. (There is no antigen identified with the d allele.)
- Another variant D antigen, DEL, has been identified in some individuals (predominantly Asians) who are classified as Rh-negative by the usual assays. While testing Rh-negative, these individuals are not likely to be sensitized by exposure to Rh-D antigens through pregnancy or transfusion (4).
- Antibodies may be produced to C, c, D, E, or e in individuals lacking the specific antigen; only D is strongly immunogenic (5).
- Isoimmunization to Rh antigens in susceptible individuals is acquired, not inherited.
- Blood typing (ABO and Rh) on all pregnant women and prior to blood transfusions
- Antibody screening early in pregnancy
- Rh immunoglobulin prevents only sensitization to the D antigen.
- For prophylaxis, Rho(D) immunoglobulin (RhIG, RhoGAM, HyperRHO, RHOphylac) given to unsensitized, Rh-negative women after the following:
- Spontaneous abortion
- Induced abortion
- Ectopic pregnancy
- Antepartum hemorrhage
- Trauma to abdomen
- Chorionic villus sampling
- Within 72 hours of delivery of an Rh-positive infant
- Given routinely at 28 weeks’ gestation
- Dose for prophylaxis:
- 50-μg dose for events up to 12 weeks' gestation
- 300-μg dose for events after 12 weeks' gestation
- Higher doses may be required in the event of a large fetal–maternal hemorrhage (>30 mL of whole blood).
- Circulating antibodies to Rh antigens (transplacentally transferred antibodies in the case of a fetus/newborn) attach to Rh antigens on RBCs.
- Immune-mediated destruction of RBCs leads to hemolysis, anemia, and increased bilirubin production.
- Transfusion of Rh-positive blood to Rh-negative recipient
- Maternal exposure to fetal Rh antigens, either antepartum or intrapartum
- Most commonly seen in the Rh-positive fetus or infant of an Rh-negative mother
Commonly Associated Conditions
- Hemolytic disease of newborn
- Hydrops fetalis
- Neonatal jaundice
- See “Erythroblastosis Fetalis” topic.