Rhesus (Rh) incompatibility is a condition where an Rh-negative mother carrying an Rh-positive fetus can produce antibodies against paternally derived Rh antigens on fetal red blood cells. These antibodies can cross the placenta, and destroy fetal red blood cells. It is a leading cause of hemolytic disease of the fetus and newborn, also known as erythroblastosis fetalis.
Effective immunoprophylaxis of Rh-negative at-risk mothers is key to primary prevention.
Intrauterine fetal transfusion is a lifesaving treatment for severely affected fetuses.
Survival rates are more than 90%.
Rh incompatibility occurs in an Rh-negative mother carrying an Rh-positive fetus. If the mother is exposed to the paternally derived Rh antigens on fetal red blood cells (RBCs) she can become sensitized and produce immunoglobulin G (IgG) antibodies, usually against the RhD antigen. These maternally derived antibodies can then freely cross the placenta, binding to and destroying fetal RBCs. This is a leading cause of hemolytic disease of the fetus and newborn (HDN or HDFN, also known as erythroblastosis fetalis), which involves progressive fetal anemia, and, if untreated, may ultimately lead to hydrops fetalis (collection of fluid in serous compartments) and death.
History and exam
Key diagnostic factors
- presence of risk factors
- history of an RhD-positive fetus in an RhD-negative mother
- fetomaternal hemorrhage
- invasive fetal procedures
- placental trauma
- omission of Rh immunoprophylaxis
- external cephalic version
- molar pregnancy
- ectopic pregnancy
1st investigations to order
- maternal blood type
- maternal serum Rh antibody screen
Investigations to consider
- maternal serum antibody titer
- paternal blood type
- paternal zygosity
- fetal ultrasound
- Doppler velocimetry of fetal middle cerebral artery (peak systolic velocity)
- fetal blood typing (from amniocentesis or maternal circulation)
- direct assessment of fetal anemia
- rosette test
- Kleihauer-Betke test/flow cytometry
unsensitized RhD-negative mother
sensitized RhD-negative mother
neonate with erythroblastosis
- Nonimmune fetal hydrops
- Parvovirus infection
- Non-RhD hemolytic disease
- FIGO/ICM guidelines for preventing Rhesus disease: a call to action
- ACOG practice bulletin no. 192: management of alloimmunization during pregnancy
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