This test is offered to Rh D Negative pregnant women 11+2 – 24 weeks gestation, but usually at 16 weeks gestation. Small amounts of the unborn baby’s DNA is present in the mother’s blood. By isolating the babies DNA from the mother’s blood, it is now possible to determine the unborn baby’s D blood group.

If the baby is predicted to be Rh D negative, then the mother will not require any prophylactic anti-D in this pregnancy before and after birth.

If the baby is predicted to be Rh D positive, or the result is inconclusive, the mother should be offered routine anti-D prophylaxis at 28 weeks gestation and following any sensitising event.

The Rh D Negative woman should be offered a Patient Information Leaflet.


Sample Requirements

6ml EDTA

Cell Free Fetal DNA Test.jpg

The request form and sample must be labelled with

  • Surname
  • First Name
  • Date of Birth
  • NHS or Hospital Number
  • The sample must be labelled, signed and dated by the person taking the blood
  • EDD must be provided on the request form
  • The sample must be taken between 11+2 – 24 weeks gestation
  • The sample tube must be in date
  • The sample must be stored at room temperature
  • The sample must reach IBGRL within 7 days of venepuncture

Unlabelled, incorrectly, altered or inadequately labelled samples will not be accepted. No specimen is considered unrepeatable.

Turnaround Times

14 days from receipt of sample.

Further external information on the cffDNA test can be found on the following link - more information