rhesus (Rh) incompatibility

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Feto-maternal rhesus (Rh) incompatibility is a situation when the maternal blood is Rh-negative blood and the fetal blood is Rh-positive (from paternal inheritance). It is a type fetomaternal blood group incompatibility and can, in turn, lead to several complications which classically includes the development of immune hydrops fetalis (IHF).

Epidemiology

The incidence rate had decreased worldwide over the years and is currently estimated to be at ~ 6 per 1000 live births (2002) .

Pathology

Rhesus incompatibility can lead to rhesus alloimmunisation where maternal antibodies may cross the placenta, bind to antigens present on the fetal erythrocytes and then cause hemolysis.

Radiographic features

Ultrasound

Doppler ultrasound can be used to detect features of a fetal anemia.

Treatment and prognosis

In severe cases, blood transfusion in utero is an option. The current day prognosis in a majority of cases is good with perinatal survival rates of more than 90% being reported; the development of hydrops fetalis can reduce the chance for a viable outcome by up to 25%. Prophylactic administration of Rho(D) immune globulin (e.g. RhoGAM) during the delivery for the first pregnancy may reduce the risk for subsequent pregnancies.

Complications

development of immune hydrops fetalis (IHF)