Determination of Fetal RhD Genotype by Gene Specific Analysis

RhD-negative mothers presenting for amniocentesis or CVS may have an RhD-positive fetus which is at risk for sensitizing its mother. This situation can result in Rh hemolytic disease of the fetus or newborn. Knowledge of whether or not the fetus is RhD- positive or negative permits you to decide whether to provide Rhogam after these procedures, later in the pregnancy, and after delivery.

Known RhD and RhCE gene DNA sequence differences in exons 7 and 10 of these genes are used to determine the RhD status of CVS, amniocyte, or blood samples by direct DNA-based testing. Two distinct regions of the RhD and RhCE genes are evaluated in order to detect known rare RhD-positive gene structure variants.

Testing requires only 1-2 ml of amniotic fluid (5 mg of chorionic villi) and 5-7 ml of maternal blood in EDTA shipped by overnight courier. Results will sent out by FAX the next working day.

In the example shown below, lane 1 shows a no DNA control, lanes 2 and 3 show RhD-positive and RhD-negative controls, respectively, and lane 4 shows a Rh-D negative fetal amniocyte sample .