Red Blood Cell Proportion in Fetal Blood (RBC Proportion in Umbilical Cord Blood)
This test measures the relative proportion of red blood cells in fetal blood, which can help assess certain blood-related conditions during pregnancy.
["Understanding fetal red blood cell proportions may aid in diagnosing or monitoring potential blood disorders in your baby."]
Key facts at a glance
- LOINC
- 67831-8
- Short code
- RBC # Plr Fetus
- Synonyms
- RBC # Plr Fetus
- Category
- chemistry
- Sample
- fluid
- Container
- Sterile tube
- Units
- N/A
- Ref low
- 4.2
- Ref high
- 5.9
- Critical range
- 2 N/A – 7 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85041
- SNOMED
- 900000000000003001
- Specimen volume
- 2-5 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h
- Hemolysis max
- 300
- TAT
- 4–24 hours
- Order
- routine
What This Test Measures
This test evaluates the ratio of red blood cells (RBCs) to other blood components in fetal circulation. It may be used to detect abnormalities in blood cell distribution, which could indicate conditions like hemolytic disease of the fetus and newborn (HDFN) or other congenital blood disorders. The measurement is typically taken from umbilical cord blood during delivery.
Why It Might Be Ordered
Your healthcare provider may order this test if you have a history of blood-related complications during pregnancy, if your baby shows signs of anemia or jaundice, or if there are concerns about fetal blood disorders. It can also be part of a broader evaluation for genetic or chromosomal conditions that affect blood cells.
Sample Collection and Preparation
A small sample of blood is collected from the umbilical cord during delivery. The blood is processed to isolate and analyze the proportion of red blood cells. This test does not require fasting or special preparation beyond standard delivery procedures.
What to Expect Before the Test
Since this test is performed during delivery, you won’t need any special preparation beforehand. Your healthcare team will ensure the sample is collected safely and accurately.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
RBC Proportion in Fetus
Frequently asked questions
What does an abnormal result mean?
Will this test affect my delivery plan?
Is there any risk or discomfort associated with this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy