Incidence of Rh D Alloimmunization

Incidence of Rh D Alloimmunization

Monica Preboth

The Committee on Practice Bulletins of the American College of Obstetricians and Gynecologists (ACOG) has published an educational bulletin on the incidence and prevention of Rh D alloimmunization (ACOG Practice Bulletin No. 4). The bulletin provides direction for the appropriate management of patients at risk to further decrease the frequency of Rh D alloimmunization. The paper appears in the May 1999 issue of Obstetrics and Gynecology.

The ACOG bulletin discusses the causes of Rh D alloimmunization, the role of anti-D immune globulin in the prevention of alloimmunization, potential shortage of anti-D immune globulin and the cost-effectiveness of Rh D prophylaxis programs. It also features a section on clinical considerations and recommendations, which includes answers to the following questions: Should anti-D immune globulin ever be withheld from a woman undergoing sterilization? How much anti-D immune globulin should be given for first trimester events and procedures? Should anti- D immune globulin be given in cases of intrauterine fetal death occurring in the second or third trimester? Should all Rh D-negative women be screened for excessive fetomaternal hemorrhage after delivery of an Rh D-positive infant?

In summary, the ACOG committee feels that reducing the incidence of Rh D alloimmunization is a prototype for the effectiveness of preventive medicine. However, the use of anti-D immune globulin is controversial in patients with threatened abortion or antenatal hemorrhage.

Based on consistent scientific evidence, the ACOG committee recommends that the Rh D-negative woman who is not Rh D-alloimmunized should receive anti-D immune globulin at the following times:

* Approximately 28 weeks of gestation, unless the father of the infant is also known to be Rh D negative

* Within 72 hours after delivery of an infant who is Rh D positive

* After the loss of a first trimester pregnancy

* After invasive procedures, such as chorionic villus sampling, amniocentesis or fetal blood sampling

Based primarily on consensus and expert opinion, the ACOG committee recommends that anti-D immune globulin prophylaxis should be considered if the patient has experienced threatened abortion, antenatal bleeding during the second or third trimester, external cephalic version or abdominal trauma.

COPYRIGHT 2000 American Academy of Family Physicians

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