One common and highly significant alloantibody implicated in HFDN is maternal Anti-D which results from exposure to fetal Rh positive red cells. Preventing alloimmunization by D-antigen is an important goal and can be achieved by removing Rh positive fetal red cells from maternal circulation using Rh-immune globulin within 72 hours of an exposure may occur during delivery or abdominal trauma in late term pregnancy.
Useful For
The fetal screen test is a qualitative test used to screen for a large fetal maternal hemorrhage (FMH) and therefore whether or not a larger dose of Rh Immune Globulin is needed. If the fetal screen test is negative, only a small bleed (<15 mL) has potentially occurred and one standard dose of Rh Immune Globulin is sufficient to suppress Rh immunization.
Method Name
Hemagglutination
Aliases
Fetal Cell Screen, Fetal Cell Screen, FMH
Specimen Type
Whole Blood
Specimen Required
Large lavender-top (EDTA) tube, approximately 7
After the patient is positively identified, the sample is drawn and fully labeled with the following information either electronically or handwritten:
- Patient’s full First and Last Name
- Date of Birth or Medical Record Number (MRN#)
- Date and Time specimen was drawn
- Blood Bank Armband Number (BBID) (see below for more information)
- Identify of the person who collected the specimen (Ex: Cerner ID or personnel initials)
All inpatients, or patients potentially receiving a transfusion, must have a blood bank armband (BBID) applied to their wrist and the Blood Bank ID (BBID) number written on the tube. This blood bank armband is a secondary patient identifier that helps ensure a safe and accurate transfusion. Specimens received without a blood bank armband will be rejected. See special instructions for more information.
Specimen Minimum Volume
1.0 – 4.0 mL
Specimen Stability Information
Stable for 12 hours at room temperature.
Rejected Due To
- If the patient’s full first and last name and date of birth are not clear, accurate, and/or readable the specimen must be rejected.
- If the Blood Bank Armband Number (BBID) from the Blood Bank Armband is missing, inaccurate, illegible and/or can not be confirmed on all inpatient and outpatient potential transfusion specimens, the specimen must be rejected and sample redrawn.
- Specimens may be rejected for insufficient quantity and/or quality reasons (Ex: Hemolysis, Clotted dilution, etc).
- If there is any doubt as to the identity of the sample, a new sample must be obtained.
Special Instructions
The test procedure requires a blood specimen collected from the mother after delivery of all products of conception. It is best to wait about an hour after delivery to allow any fetal blood to mix
thoroughly in the maternal circulation, but the sample should be collected as soon as possible thereafter.
Performing Laboratory
Glens Falls Hospital Laboratory
Reference Values
Positive test: After examining five low-power fields, if five or more agglutinates of red blood cells are observed, the test is positive and indicates the presence of D-positive fetal red blood
cells in possibly significant numbers in the maternal blood.
Negative test: After examining five low-power fields, if four or fewer agglutinates of red blood cells are observed, the test is negative, indicating that a large feto-maternal hemorrhage did
not occur.
Day(s) and Time(s) Performed
24 hours 7 days a week
Analytical Time
STAT turn around time approximately 1 hour.
Routine inpatient samples around time is approximately 2- 4 hours.
Specimen Retention Time
10 Days
Reflex Tests
A Fetal Stain will reflex on all positive Fetal Screen results. Fetal stain will be sent to Albany Medical Center and is necessary to determine how many doses of Rh Immune Globulin are needed.
Analytical Time
STAT turn around time approximately 1 hour.
Routine inpatient samples around time is approximately 2- 4 hours.