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Published: August 9, 2026Updated: August 16, 2026

This test determines a newborn's blood type (ABO and Rh) after a transfusion reaction to ensure safe future blood transfusions.

Quick summary

{"Checks the baby's blood type (A, B, AB, or O) and Rh factor (positive or negative)","Performed after a transfusion reaction to confirm the correct blood type","Helps prevent dangerous reactions in future blood transfusions","Requires a small blood sample from the baby","Results are critical for safe blood transfusion practices in newborns"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
50773-1
Short code
ABO Rh newborn post-transfusion
Synonyms
ABO + Rh p transf rx Bld NB
Category
chemistry
Sample
whole-blood
Container
EDTA lavender/purple top tube or pink top tube (EDTA for blood bank testing)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
0–1 years
Method
Serological typing using tube agglutination or gel column assay with anti-A, anti-B, anti-AB (group O cells) and anti-D (Rh) reagents
CPT
86900 (ABO typing); 86901 (Rh typing)
SNOMED
365689006 (blood group antigen measurement)
Specimen volume
2-3 mL whole blood
Stability
Room temperature (20-25°C): 72 hours; Refrigerated (2-8°C): 7 days; Do not freeze
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
1–4 hours
Order
routine

What is this test?

The ABO and Rh blood type test is a laboratory test that identifies the specific blood group and Rh factor in a newborn's blood. This test is specifically performed after a transfusion reaction has occurred to verify the baby's actual blood type and ensure that any future blood transfusions are given with the correct, compatible blood type.

Why is this test performed?

When a newborn experiences a transfusion reaction (an adverse response to a blood transfusion), doctors need to confirm the baby's exact blood type. This helps determine whether the reaction was caused by receiving the wrong blood type or another issue. Knowing the correct blood type is essential for providing safe blood products in the future.

How is the test done?

A small blood sample is taken from the newborn, usually from a vein or sometimes from the heel. The blood sample is then sent to the laboratory where it is tested to determine the ABO group (A, B, AB, or O) and the Rh factor (positive or negative).

Understanding blood types

Blood type is determined by the presence or absence of certain antigens on red blood cells. The ABO system classifies blood as A, B, AB, or O. The Rh system classifies blood as Rh-positive or Rh-negative. For example, a baby might be A positive, B negative, O positive, or AB negative, etc. This information is crucial for matching blood donations safely.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: whole-blood

No fasting required. Collect specimen before transfusion if possible, or wait 24-72 hours post-transfusion to avoid interference from donor red blood cells. For newborns, cord blood or peripheral venipuncture sample is acceptable. Document recent transfusion history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Is this test safe for my baby?
Yes, this test is very safe. Only a small amount of blood is needed, and the collection is done by trained healthcare professionals experienced with newborns. The discomfort is minimal and temporary.
How long does it take to get results?
Results are typically available within a few hours to one day, depending on the laboratory. Your healthcare team will inform you of the results as soon as they are available.
What if my baby's blood type is rare?
If your baby has a rare blood type, the blood bank will ensure that properly matched blood products are available for any future transfusions. Rare blood types are documented and special arrangements can be made if needed.
Will my baby need more blood tests after this?
Your healthcare team will determine if additional tests are needed based on the results and the baby's condition. This test primarily helps ensure safe future transfusions.
Does this test affect breastfeeding?
No, this test does not affect breastfeeding. You can continue to breastfeed normally as directed by your healthcare provider.
  1. 1
    American Red Cross - Blood TypesSource
  2. 2
    Mayo Clinic - Blood TransfusionSource
  3. 3
    AABB - Transfusion ReactionsSource

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.

Medical Disclaimer

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 16, 2026. · Read our editorial policy