Blood group and Rh testing: Questions About Your Results

Pregnancy blood tests usually record both your ABO blood group and whether you are RhD positive or negative. They also check for red cell antibodies. These are related results, but they are not interchangeable, and being RhD negative does not mean you or your baby is ill.

Separate blood group from antibodies

ABO groups include A, B, AB and O. RhD describes whether a particular marker is present on red blood cells. Antibodies can develop after exposure to red cells with a different blood group, for example through pregnancy or a transfusion.

Some antibodies can cross the placenta and damage a baby’s red cells if the baby carries the matching marker. Other antibodies, including those involving the c or Kell blood groups, can matter as well as anti D. An RhD positive result therefore does not remove the need for the antibody screen.

Ask for the actual result names and whether any antibody needs further assessment. The pregnancy blood test guide explains how these checks fit alongside other booking tests.

Ask whether prevention applies

If you are RhD negative, have not already formed immune anti D antibodies and your baby may be RhD positive, the team may offer anti D immunoglobulin. This helps prevent sensitisation, which means your body forming its own anti D antibodies.

Some services can test the baby’s predicted RhD group using your blood. Availability and the care plan vary. If immune anti D antibodies are already present, preventive injections do not undo them; specialist monitoring may be needed instead.

Ask when routine prevention is planned and whether a baby’s RhD result changes it. Confirm what will be checked after birth. Do not assume that an injection in pregnancy completes every possible part of the plan.

Report bleeding or an injury promptly

Contact maternity care after vaginal bleeding or an injury to your abdomen and tell them your blood group if known. Certain procedures also require assessment for additional anti D. When indicated after a sensitising event, it is ideally given within 72 hours, so do not wait for a routine appointment.

The team decides whether it is needed based on the event and pregnancy stage. Contact them even if more time has passed. A recent routine injection does not mean you can ignore a new event.

Keep the information available

Keep your results and any antibody information with your maternity record, particularly when changing hospitals or travelling. The prenatal appointment schedule guide can help you track the next blood check.

Before leaving, confirm whether you need prevention, additional testing or specialist follow up. These are different plans, and knowing which applies makes the next step clearer.