Non-Invasive Prenatal Test for Fetal RhD Status Demonstrates 100% Accuracy

By LabMedica International staff writers
Posted on 03 Mar 2025

Image: The technology has the unique ability to detect challenging RhD variants that are typically excluded by other commercial tests (Photo courtesy of BillionToOne)

In the United States, approximately 15% of pregnant individuals are RhD-negative. However, in about 40% of these cases, the fetus is also RhD-negative, making the administration of RhoGAM unnecessary. Now, a non-invasive prenatal test (NIPT) for determining fetal RhD status has demonstrated 100% accuracy in a large clinical study, enabling healthcare providers to use the results to guide RhoGAM administration.

The study demonstrated that BillionToOne’s (Menlo Park, CA, USA) proprietary next-generation sequencing (NGS) combined with Quantitative Counting Template (QCT) technology provides definitive results with perfect accuracy. The study included challenging variants, such as RHDѰ and RHD-C-DE, which are often omitted in other studies, ensuring a true reflection of clinical performance. The test achieved 100% sensitivity, specificity, positive predictive value, and negative predictive value across 401 pregnancies when compared to neonatal RhD serology, considered the gold standard. One of the standout features of BillionToOne's technology is its ability to detect difficult RhD variants, a capability that sets it apart from other commercial tests.

The study also demonstrated 100% accuracy in identifying fetal RHDѰ variants, which occur in approximately 25% of Black Rh-negative individuals, as well as RHD-CE-D hybrid variants. Many other commercially available fetal RhD NIPTs cannot detect the fetal RhD status in cases where these variants are present, thus limiting the test's applicability in the broader obstetric population. This feature is particularly critical for ensuring accurate testing across diverse populations, especially in the US. The research confirms the clinical validity of the test, with healthcare providers already using the results to guide RhoGAM administration. Over time, as clinicians grew more confident in the test's accuracy, there was a noticeable reduction in unnecessary RhoGAM administration for pregnancies with RhD-negative fetuses.

This marks BillionToOne's third peer-reviewed publication on its fetal antigen assay and the second published in The Journal of Obstetrics and Gynecology. This latest publication follows a recent update from the American College of Obstetricians and Gynecologists (ACOG), which supported the use of non-invasive cell-free DNA screening for fetal RhD, especially during RhoGAM shortages and as an alternative in alloimmunized pregnancies when amniocentesis is declined. ACOG’s updates referenced BillionToOne's prior studies.

"By accurately identifying fetal RhD status, we can avoid unnecessary RhoGAM administration in approximately 40% of patients carrying RhD-negative fetuses," said Dr. Julio Mateus Nino, MD, Maternal & Fetal Medicine, first author of the study. "BillionToOne's QCT technology also provides critical information for patients with RhD alloimmunization, giving physicians the tools to guide antenatal management based on actual fetal genotype rather than assumption. This is a meaningful advancement in personalized prenatal care that benefits both patients and healthcare systems."

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