Which women are eligible for the RHD NIPT?
All women who are RhD negative with no preformed anti-D antibodies should be recommended RHD NIPT testing between 12-26 weeks gestation of pregnancy.
This includes women with a singleton or multiple pregnancy.
Women may be offered RHD NIPT up to 32 weeks as this would still limit unnecessary RhD Ig at 34 weeks gestation and for sensitising events
Weak and Partial D
Is the woman a weak D type 1, 2, or 3?
Yes → Treat as RhD positive.
No → Treat as RhD negative and offer RhD Ig prophylaxis at 28, 34 weeks and for all sensitising events . Depending on the individual RHD NIPT offered by the laboratory and the type of maternal RhD variant, it may not be possible to determine the fetal RhD type. The case can be discussed with the testing laboratory pathologist to determine if RHD NIPT should be performed.
Repeat antibody screen between 26 – 28 weeks gestation.
If necessary, seek further advice and/testing through the Lifeblood’s Red Cell Reference Lab , Queensland.
RhD negative women with clinically significant antibodies (D, C, c, E, K, k, Fy) or history of Haemolytic Disease of the Fetus or Newborn (HDFN)
All women with clinically significant antibodies or history of HDFN should be referred to a fetomaternal specialist regardless of antibody type and titre.
All women with clinically significant antibodies should have a specimen referred to the Lifeblood’s Red Cell Reference Lab , Queensland for NIPA testing.
Does the woman have anti-D antibodies?
No → Refer for RHD NIPT in addition to the Lifeblood’s Red Cell Reference Lab , Queensland.
If the results of the RHD NIPT are inconclusive, not reported or RhD positive fetus, RhD Ig therapy is recommended.
RhD negative women
All RhD negative women are recommended for RHD NIPT testing between 12-26 weeks gestation.
Women who present later than 26 weeks or where a result is not available may be offered testing up to 32 weeks gestation as this would still prevent unnecessary RhD Ig at 34 weeks and for sensitising events if the fetus is predicted to be RhD negative.
This includes women with a singleton or multiple pregnancy as provided one of the fetuses is RhD positive, RhD Ig will be recommended.
Specimen Collection
- Is the request form complete and on the correct form? (No – contact the requesting clinician to complete the correct form and required information)
- Is the woman between 12-26 weeks (may be considered up to 32 weeks) according to the estimated due date? (No – contact requesting clinician)
- Verify the woman’s identity by asking her to verbally (where possible) confirm her name and date of birth.
- Collect the specimen using the correct tube and order of draw according to the test manual. Label immediately following collection with a minimum of 2 patient identifiers (Full name, Date of Birth and a Medical Record Number or address if available). Date and sign the specimen. Do not reopen the tube once the specimen has been collected.
- Ask the woman to visually inspect the specimen and verify all details are correct. Any discrepant details will result in the specimen being rejected. Where the woman is unable to complete the check, another staff member or patient representative must complete this.
- Place the sample and the form in the specimen bag and transport to pathology reception or place in appropriate storage until transport to the specimen reception.
Specimen Reception
- Check that the specimen type is correct, details on the specimen label and the form are correct and match identically. If there is a discrepancy or the incorrect specimen tube has been used notify the collector/requesting clinician. The specimen will need to be recollected.
- Register the sample in the Laboratory Interface System (LIS) using the test code for RHD NIPT. This will still need to be completed if the specimen is rejected to enable tracking.
- Transfer to processing department or if processing at an external laboratory pack for sending according to the Standard Operating Procedure (SOP) Manual for specimens for processing in an external laboratory.
Specimen Processing
- As per the RHD NIPT provider’s SOP.
Result and Reporting
Once a result is complete it must be checked by a second person. The result should be reported as either not reported, inconclusive, RhD positive fetus or RhD negative fetus.
The result must clearly distinguish between the maternal and fetal blood group results.
Send the report to the requesting clinician or the referring laboratory. It is recommended that the results are also uploaded to the My Health Record.
If the specimen was sent by a referring laboratory, the referring laboratory must record the result in the Laboratory Information System (LIS) and ensure that the result is provided to the requesting clinician.
Not Reported
Specimen does not contain minimum required details, haemolysed on arrival, inadequate sample, unable to extract sufficient DNA, EDD indicates less that 12 weeks gestation.
Contact the requesting clinician or the referring laboratory. The sample will need to be recollected if time allows or the woman recommended for RhD Ig prophylaxis.
Inconclusive
Inconclusive samples should be re-run through the analyser. If the second run is inconclusive the result is reported as inconclusive.
Notify referring laboratory or clinician of the result.
RhD Ig prophylaxis is recommended.
RhD Positive Fetus
RhD Ig prophylaxis is recommended.
Repeat antibody screen at 28 weeks gestation.
RhD negative Fetus
RhD Ig prophylaxis is not recommended.
Repeat antibody screen at 28 weeks gestation.
Cord Blood Specimen
All RHD NIPT test results should be confirmed with a cord blood test prior to administration of RhD Ig if indicated (Rh positive fetus, unknown or inconclusive result). Where there is discordant cord blood result, a capillary blood specimen must be collected from the baby to confirm the baby’s blood group.
If a discordant cord blood result is confirmed by the capillary sample from the baby this should be reported through the haemovigilance monitoring system and in the LIS.
In the event of a false-negative RHD NIPT result – RhD Ig is to be administered to the woman within 72 hours of the birth of the baby.
The woman and primary clinician should be notified if not yet aware to enable follow-up and documentation in the antenatal/healthcare record.
What is a sensitising event?
If you are RhD negative and your baby is RhD positive, small numbers of the baby’s red cells can cross the placenta into your blood and cause an immune reaction. This is known as sensitisation.
This occurs more commonly during the 3rd trimester of pregnancy and at the birth of your baby.
There are additional events that may cause higher numbers of the baby’s red cells to cross into the mother’s blood. This is known as a sensitising event, and may be caused by;
- during some tests you may have during your pregnancy (such as chorionic villus sampling (CVS) or amniocentesis)
- after miscarriage or termination
- obstetric haemorrhage (heavy, frequent bleeding during pregnancy)
- after an injury or accident to your abdomen
- if your baby is in a breech position and you have an external cephalic version (where doctors turn the baby around inside the womb)
- during labour
- from an ectopic or molar pregnancy