Free Fetal DNA Testing to Guide Early Intervention in the Management of the Kell Alloimmunized Pregnancy

Key Points Free fetal DNA can accurately be used to determine the fetal red cell genotype. A false positive elevation of the middle cerebral artery peak systolic velocity can occur in the early second trimester in a red cell alloimmunized pregnancy. In most cases, fetal intrauterine transfusions should be limited to pregnancies with a documented positive fetal genotype for the involved antigen.