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Immunology & Autoimmune
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Currently under review
Pending specialist review and validation.
The fetal cells test measures the proportion of fetal red blood cells circulating in a maternal blood sample. It is commonly performed using the Kleihauer-Betke acid elution method, which highlights cells containing fetal hemoglobin on a microscope slide for counting.
Clinicians use this test around delivery, after abdominal trauma, or following invasive procedures in pregnancy to assess fetomaternal hemorrhage.
Detecting fetal cells that have entered your bloodstream helps your care team estimate the degree of fetomaternal bleeding. For people who are Rh negative, this information guides the dose of Rh immune globulin to lower the risk of Rh sensitization in the current and future pregnancies.
The test can also inform management after trauma, placental complications, or procedures, and may prompt additional monitoring for you and your baby.
Your report will indicate whether fetal cells are present and provide an estimate of their proportion. A trace amount can be seen even without complications, while higher results suggest more significant fetal blood transfer.
Your clinician will interpret the result together with the timing of the sample, your Rh type, delivery or injury details, and any procedures. If needed, you may receive Rh immune globulin, have repeat testing, or undergo additional evaluation, but most results are addressed with routine care.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Collecting blood too soon after a bleeding event may miss redistribution, and collecting much later can underestimate results as fetal cells clear from circulation.
Conditions that increase fetal hemoglobin in adults, such as hereditary persistence of fetal hemoglobin or some thalassemias, can cause falsely high results with the Kleihauer-Betke method.
Transfusion can dilute or complicate interpretation, and large maternal blood loss may alter calculated estimates of fetal cell proportion.
Twins or placental problems can increase the chance of fetomaternal bleeding, and results may lead to adjusted management or dosing decisions.
Manual Kleihauer-Betke staining and flow cytometry have different sensitivities and potential inter-observer variability, which can affect reported values.
Prior Rh immune globulin can influence some screening assays used with this test algorithm, so telling your care team about recent doses helps accurate interpretation.
References