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Kleihauer-Betke stain; Flow cytometry – fetal-maternal erythrocyte distribution; Rh incompatibility – erythrocyte distribution
The fetal-maternal erythrocyte distribution test is used to measure the number of the unborn baby’s red blood cells in a pregnant woman’s blood.
How the Test is Performed
A blood sample is needed.
How to Prepare for the Test
No special preparation is necessary for this test.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
Rh incompatibility is a condition that occurs when the mother’s blood type is Rh-negative (Rh-) and her unborn baby’s blood type is Rh-positive (Rh+). If the mother is Rh+, or if both parents are Rh-, there is no reason to worry about Rh incompatibility.
If the baby’s blood is Rh+ and gets into the mother’s Rh- bloodstream, her body will produce antibodies. These antibodies could pass back through the placenta and harm the developing baby’s red blood cells. This can cause mild to serious anemia in the unborn baby.
This test determines the amount of blood that has been exchanged between the mother and fetus. All Rh- pregnant women should get this test if they have bleeding or a risk of bleeding during the pregnancy.
In a woman whose blood is Rh incompatible with her infant, this test helps find out how much Rh immune globulin (RhoGAM) she must receive to prevent her body from producing abnormal proteins that attack the unborn baby in future pregnancies.
Normal Results
In a normal value, no or few of the baby’s cells are in the mother’s blood. The standard dose of RhoGAM is enough in this case.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
In an abnormal test result, blood from the unborn baby is leaking into the mother’s blood circulation. The more of the baby’s cells there are, the more Rh immune globulin the mother must receive.
Risks
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
FAQ
How do you test for fetal-maternal hemorrhage?
- The Kleihauer Betke test is utilized to determine if there is fetal blood in maternal circulation, with a threshold of 5 mL. The rosette test is performed by incubating the Rh-negative maternal venous whole blood sample with anti-Rho(D) immune globulin.
Which test differentiates fetal and maternal blood cells?
- The alkali denaturation test, also known as A or Apt test, is a medical test used to differentiate fetal or neonatal blood from maternal blood found in a newborn’s stool or vomit, or from maternal vaginal blood.
What are maternal blood and fetal blood?
- The placenta is a unique vascular organ that receives blood supplies from both the maternal and the fetal systems and thus has two separate circulatory systems for blood: (1) the maternal-placental (uteroplacental) blood circulation, and (2) the fetal-placental (fetoplacental) blood circulation.
What does a positive Kleihauer Betke test mean?
- What is a positive Kleihauer-Betke test? A positive KB test means there is fetal blood in the maternal circulation. The sensitivity of the KB test is 5 mL, meaning a fetomaternal hemorrhage of less than 5 mL between the fetus and the pregnant individual’s circulation may not be detected with this method.
What is a positive rosette test?
- The rosette test is a screening test for FMH that detects fetal D+ red cells in maternal Rh-negative blood. If the rosette test is positive, follow-up testing is done to quantitate the FMH, eg, a Kleihauer-Betke acid elution test or flow cytometry.
What is the principle of the rosette test?
- The rosette test demonstrates the number of D-positive cells in a D-negative suspension using an anti-D reagent. The anti-D binds to D-positive fetal RBCs, and when indicator D-positive RBCs are added rosettes are formed. This method has an FMH detection limit of about 10 mL.
How do fetal RBC differ from maternal RBC?
- In maternal blood, fetal RBCs can be identified due to the differences between them and adult RBCs and these are fetal hemoglobin (HbF) presence, lack of the carbonic anhydrase (CA), and the presence of a particular group antigen.
What is a Kleihauer test in pregnancy?
- In maternal trauma, the Kleihauer-Betke (KB) test has traditionally been used to detect transplacental hemorrhage (TPH), so that Rh-negative women could receive appropriate Rh immune prophylaxis.
What is the meaning of maternal blood?
Related Definition
- Maternal Blood means the peripheral blood collected from the birth mother of the Child, which has been drawn by observing standard phlebotomy procedures taken within seven (7) days before or after the birth of the Child. Maternal Blood means blood samples taken from a pregnant woman.
How does maternal and fetal blood not mix?
- The placenta protects the mother and fetus
- One of the placenta’s jobs is to make sure blood from the mother and fetus never mixes. The placenta acts as an exchange surface between the mother and the fetus. Nutrients and oxygen are passed over by diffusion only.
What happens if maternal and fetal blood mix?
- If a baby’s and mother’s blood are incompatible, it can lead to fetal anemia, immune hydrops (erythroblastosis fetalis), and other complications. The most common type of blood type incompatibility is Rh disease (also known as Rh incompatibility). The Rh factor is a protein on the covering of red blood cells.
When do you do a Kleihauer test?
- This test should be performed and any subsequent Anti-D required administered within 72 hours of delivery, sensitizing event, or invasive procedure.
How is the Kleihauer Betke test done?
- A blood sample from the mother is made into a smear on a glass slide, then the slide is flooded with acid. Maternal hemoglobin (presumably hemoglobin A as in most adults) dissolves away and the fetal hemoglobin F remains intact. Then, the slide is washed, stained, and read.
