RhD IncompatibilityRhesus (Rh) D blood group incompatibility between a pregnant woman and her fetus is a significant problem due to the possibility of maternal alloimmunization and consequent hemolytic disease of the newborn. Alloimmunization most frequently occurs, when an RhD negative mother is exposed to red blood cells of an RhD positive fetus, producing maternal antibodies against the RhD antigen. Although the pregnancy in which alloimmunization first occurs results in an unaffected child, future children are at substantial risk of anemia and in the worst cases, fetal death. In the United States alone, the frequency of RHD incidence occurs at about 10-15% of pregnancies.
Since the 1960’s, routine administration of anti-D immunoglobulin to RhD negative women at 28 weeks and after the birth of child has helped prevent maternal alloimmunizations. Today, this prophylactic treatment prevents alloimmunzation in 96% of cases. For the remaining 4% of women, approximately 20,000 pregnancies in the US per year, it is important to establish the RhD type of the fetus. This is frequently performed by amniocentesis, between weeks 16-20 pregnancy. If testing shows that the fetus is RhD negative, no further testing is required. If positive, the pregnancy is closely monitored to ensure the health of the baby.
Using Sequenom’s SEQureDxTM technology, a noninvasive test using a maternal blood sample has been developed to analyze fetal RhD, before amniocentesis or administration of anti-D immunoglobulin is required. Sequenom believes this has the diagnostic potential to eliminate unnecessary amniocentesis in cases of RhD alloimmunized women and to potentially prevent unnecessary administration of anti-D immunoglobulin. Developing diagnostic technologies that will provide clinicians with early, reliable results will give clinicians sufficient time to plan for further tests or treatment that can reduce the risk to the fetus and improve pregnancy outcome. |