Advances in ultrasonography have led to new methods of management of alloimmunization in pregnant women and may allow for a more thorough and less invasive workup with fewer maternal and fetal risks, according to a practice bulletin by the American College of Obstetricians and Gynecologists (ACOG).

In a study of 111 fetuses at risk for anemia secondary to red cell alloimmunization, researchers used Doppler ultrasonography to measure peak systolic velocity in the fetal middle cerebral artery. Values of more than 1.5 times the median for gestational age were predictive of moderate to severe fetal anemia (sensitivity = 100 percent; specificity = 88 percent). However, ACOG notes that correct technique is critical and that this procedure should be used only by physicians with adequate training and clinical experience.

The initial management of a pregnancy involving an alloimmunized patient is determination of the paternal erythrocyte antigen status. If the father is negative for the erythrocyte antigen in question and if it is certain that he is, indeed, the father, further assessment and intervention are unnecessary.

Administration of Rh_o(D) immune globulin (Rhogam) is indicated only in Rh-negative women who were not previously sensitized. At the first prenatal visit, all pregnant women should be tested for ABO blood group and Rh-D type, and they should be screened for erythrocyte antibodies. These assessments should be repeated in each subsequent pregnancy. The American Association of Blood Banks also recommends repeated antibody screening before administration of Rh_o(D) immune globulin at 28 weeks' gestation, at the time of any event in the pregnancy, and in the postpartum period.

The full ACOG report was published in the August 2006 issue of Obstetrics & Gynecology.