Nucleated Red Blood Cells (nRBC)

Typically only found in the bone marrow, during pregnancy a small amount of nucleated red blood cells is considered normal. This increase may have a protective mechanism for childbirth, blood loss, and overall maternal function. 

nRBC Testing

The nucleated red blood cells (nRBC) test measures the number of red blood cells with a nucleus in a blood sample. 

Nucleated RBCs are immature red blood cells with a nucleus and DNA. As RBCs mature, they lose their nucleus and become conclave in structure. Nucleated RBCs are generally only found in the bone marrow and are the precursors to reticulocytes. The other name for these cells is erythroblasts. 

Many of the nucleated RBCs found in maternal circulation are from the fetus. A small amount of fetal blood and tissue cells, including trophoblasts, lymphocytes, granulocytes, and nucleated red blood cells, are also present in maternal circulation.

Elevations in these cells past gestational norms can indicate placental dysfunction.

nRBC in Pregnancy

Nucleated RBCs in the maternal circulation can be seen as early as six to eight weeks. This production steadily increases throughout pregnancy, with a sharper rise in the last few weeks of pregnancy before the onset of labor.

This rise in nucleated RBCs in the last few weeks of pregnancy may be the underlying connection to the increase in RDW. This is currently theoretical but could be a protective mechanism for blood loss during childbirth.

High nRBC in Pregnancy

>4% in the first trimester can be a predictive biomarker for high-risk pregnancy complications associated with placental dysfunction.

>13% may be associated with pregnancy complications. Studies have shown that an elevation of nRBC counts may be a predictive marker for idiopathic IUGR and other pregnancy complications.

Please read the Red Blood Cell Size Distribution Width (RDW) article. 

Most Common Causes of High nRBC in Pregnancy

• Hypoxia
• Sleep Apnea/Snoring
• Asthma/Lung Disease
• Recent Move to Higher Altitude
• Placental Dysfunction
• Myeloproliferative Disease (Polycythemia)
• Excess Erythropoietin Production 
• Thalassemia
• Hemolytic Anemia
• Sickle Cell Anemia
• Severe Infections
• Heavy Metal Exposure
• Internal Bleeding

Low nRBC in Pregnancy

Causes of decreased production of nRBCs in pregnancy are not typically addressed as a specific medical issue.

Any condition in which there is an overall reduction in RBC production can cause a decrease in nRBC release into circulation. Please read the Red Blood Cell Count (RBC) article, as well as the Red Blood Cell Size Distribution Width (RDW) article. 

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Medical Disclaimer:
This content is for educational purposes only and is intended for licensed medical professionals. It is based on current research, subject to change, and not intended to diagnose, treat, or prevent any medical condition. This information does not replace consultation with a qualified healthcare provider. Seek professional medical evaluation and treatment from a licensed provider. Use of this information is at your own risk.​

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