Accuracy of non-invasive fetal Rh genotyping from maternal blood

Abstract

CHAD A. GROTEGUT, JOHN P. GAUGHAN, OSSIE GEIFMAN-HOLTZMAN, Temple University School of Medicine, Obstetrics, Gynecology and Reproductive Sciences, Philadelphia, Pennsylvania, Temple University School of Medicine, Biostatistics, Philadelphia, Pennsylvania OBJECTIVE: To determine the reported accuracy of non-invasive fetal Rh genotyping from maternal blood. STUDY DESIGN: A PubMed search of the literature describing fetal Rh determination from maternal blood was conducted. From each study, we determined the fetal Rh genotype tested, the source of the fetal DNA (maternal plasma, serum or fetal cells), gestational age, and confirmation of fetal Rh type. The sensitivity and specificity of the Rh typing were calculated and the presence of alloimmunization and exclusions due to Rh gene rearrangements were noted. RESULTS: We found 25 English-written publications reporting non-invasive Rh typing using fetal DNA obtained from maternal blood. Gestational age at time of testing ranged from 12 to 41 weeks. A total of 2122 correct fetal RhD genotyping were documented out of 2240 tested (94.7%). When excluding for reported RhD gene rearrangements, the testing accuracy increased to 97.5% (2122 out of 2186 tested). Fetal RhD was determined correctly in 13 of 28 (46.4%) alloimmunized pregnancies. For other Rh groups, a total of 97/98 (98.9%) correct fetal RhE/e genotyping and a total of 79/91 (86.8%) fetal RhC/c genotyping were reported. Alloimmunization status was reported in 4 studies and in 21 studies testing was performed on Rh negative mothers. When looking at the years 1993-2000 compared to 2000-2005, 174/216 (80.5%) vs. 1948/1970 (98.8%) correct fetal Rh genotyping were reported. CONCLUSION: Accurate non-invasive fetal Rh determination using maternal peripheral blood is possible and can be applicable to Rh prophylaxis and to the management of Rh alloimmunized pregnancies. Improvements of the technique and further study of structure and rearrangements of the RhD gene S136 SMFM Abstracts