Fetal RHD genotyping after bone marrow transplantation

Area of Science:

• Obstetrics and Gynecology
• Genetics
• Immunology

Background:

• Noninvasive prenatal fetal RHD genotyping is crucial for managing RhD-alloimmunized pregnancies.
• Potential causes for false-positive or false-negative results exist.
• This report details two cases complicated by prior bone marrow transplantation (BMT).

Observation:

• Two women with a history of allogeneic BMT received RhD-positive (D+) male sibling transplants.
• Both women had RhD-positive fetuses, with one developing anti-D antibodies during pregnancy.
• Maternal plasma DNA testing for fetal RHD was positive in both cases, yet one neonate was RhD-negative (D-).

Findings:

• False-positive fetal RHD genotyping results can occur in RhD-positive (D+) women who received RhD-negative (D-) bone marrow transplants.
• Circulating cell-free DNA from nonhematopoietic tissues can lead to inaccurate results.
• Incorrect fetal sex determination is also possible with male donors and female fetuses.

Implications:

• Healthcare professionals and laboratories must be aware that allogeneic BMT can cause false-positive fetal RHD genotyping.
• Consideration of BMT history is vital for accurate interpretation of cell-free DNA-based fetal RHD testing.
• Recommendations include administering RhD-negative (D-) blood products to young females undergoing BMT from D- donors.