Red Blood Cell Distribution Width in Fetal Blood (Autoanalyzer Method)
This test measures the variation in size of red blood cells (RBCs) in fetal blood, which can help assess potential blood-related conditions in the fetus.
["Measuring RBC size variation may support prenatal health evaluations."]
Key facts at a glance
- LOINC
- 62247-2
- Short code
- Erythrocyte DistWidth Bld Fetus Auto
- Synonyms
- Erythrocyte DistWidth Bld Fetus Auto
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- 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
- Method
- automated-count
- CPT
- 85041
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order this test if there are concerns about fetal anemia, blood flow issues, or genetic conditions that could affect red blood cell production or size. It may also be part of routine prenatal monitoring in certain cases.
What Does the Test Involve?
A small blood sample is taken from the fetus, often through procedures like a cordocentesis or amniocentesis. The sample is analyzed to determine the range of RBC sizes, which is then reported as the red blood cell distribution width (RDW).
What Do Results Mean?
The results provide a measure of RBC size variability, which can indicate whether RBCs are consistently produced or if there is an underlying issue affecting their development. Abnormal results may signal conditions requiring further investigation.
What Are Common Causes of Abnormal Results?
Elevated RDW in fetal blood could be linked to conditions like fetal anemia, thalassemia, or other genetic disorders affecting RBC production. Lower-than-expected RDW might suggest normal RBC uniformity or specific genetic factors.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
RDW-Fet
Frequently asked questions
Why might my healthcare provider recommend this test during pregnancy?
How is the blood sample collected for this test?
What are the typical follow-up steps if my RDW result is abnormal?
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