As more patients and providers become aware of the risks of amniocentesis, many are choosing to use cell-free fetal DNA (cffDNA) testing to determine fetal antigen status. Unlike the traditional amniocentesis, the cffDNA testing carries no risk of fetal-maternal hemorrhage, increasing titers, chorioamnionitis, or fetal loss. This simple blood draw is a noninvasive way to find out whether a baby is antigen positive or negative. Fetal DNA is extracted from the mother’s blood and tested for the antigen.
A negative result can greatly relieve patient anxiety, while a positive result can help patients prepare for increased prenatal appointments and the possibility of a longer hospital stay after birth. For women with anti-D, anti-c, anti-C, anti-E, anti-e, or anti-K, if the fetus is antigen negative, weekly MCA scans are unnecessary and the pregnancy can proceed as usual without an early induction of labor. If the fetus is antigen positive, the fetus is at risk for HDFN and weekly MCA scans may be required if titers reach the critical threshold. An at risk baby would be delivered at an earlier gestation (37-38 weeks). The results can also help determine if there is a need for RhD Immune Globulin (RhoGAM) in an Rh- mother.
Overall accuracy of the test is over 99%. It may need to be repeated if it is performed at an early gestation (9-14 weeks) or if the baby is female.
For additional articles about cffDNA testing, see our Additional Reading by Topic page.
Regardless of where you are located at, you may have your blood drawn at any laboratory and shipped to any of the labs listed below for testing.
While the link below is only for anti-D, the Red Cross is also doing a study for other antigens. Ask your doctor to be enrolled if you have antibodies against the c, C, e, E, or K antigens. Australian Red Cross Non-Invasive Prenatal Analysis (NIPA) for RhD