Blood Group & Rh in Pregnancy — What It Means
Informational only. Antenatal results should always be discussed with your obstetrician, who interprets them for your specific pregnancy.
This test finds your ABO blood group. It also shows if the Rhesus (Rh) factor protein sits on the surface of your red blood cells. Knowing your blood group is key for safe transfusion in an emergency. It also flags Rh-negative women. They may need anti-D injections. These help prevent a blood problem in the baby in future pregnancies.
First trimester
Last reviewed: 2026-08-16
When is it done?
You have this at your first antenatal visit, usually before 12 weeks. The result is recorded for your whole pregnancy.
Why is it done in pregnancy?
Knowing your blood group is key for safe transfusion in an emergency. It also flags Rh-negative women. They may need anti-D injections. These help prevent a blood problem in the baby in future pregnancies.
About the reference range
Blood group and Rh type are fixed features of your body. They are not measured values with a reference range. So there is no trimester range to report.
What to discuss with your obstetrician
If you are Rh-negative, ask your obstetrician about the timing and need for anti-D injections. Also ask if your partner's blood group should be tested.
Questions to ask your obstetrician
About this result
- What does my Blood Group & Rh result mean for me and my baby at this stage of pregnancy?
- Is my Blood Group & Rh being read against a pregnancy-specific range?
What to do next
- Based on my Blood Group & Rh, is there anything you would suggest I do or change during this pregnancy?
About retesting
- Will my Blood Group & Rh be checked again later in the pregnancy, and if so, when?
The bigger picture
- How does my Blood Group & Rh fit with the rest of my antenatal checks?
Frequently asked questions
- What does Rh-negative mean?
- Rh-negative means the Rh protein is not on your red blood cells. It is not a disease or a fault. It simply means your Rh status needs careful care in pregnancy. This matters if your baby may be Rh-positive.
- What is anti-D immunoglobulin and why might I need it?
- Anti-D is an injection given to Rh-negative women. It stops you making antibodies against Rh-positive red cells from your baby. It is usually given at certain points in pregnancy. It is also given after birth if your baby is Rh-positive.
- Does blood group affect pregnancy if I am Rh-positive?
- Being Rh-positive means you have the Rh protein. You are not at risk of Rh sensitisation. Your blood group may still matter for a safe transfusion if needed.
- Will I need anti-D if I have a miscarriage or any bleeding in pregnancy?
- Rh-negative women may need anti-D after certain events. These include miscarriage, bleeding with a threatened miscarriage, amniocentesis, or a blow to the belly. Discuss any such event with your obstetrician promptly.
- Can an Rh-negative mother have a healthy baby?
- Yes. With good antenatal care, Rh-negative women routinely have healthy pregnancies and babies. This includes anti-D given at the right time when it is needed.
Sources
- RCOG (2011) — RCOG Green-top Guideline No. 22: The Use of Anti-D Immunoglobulin for Rhesus D Prophylaxis
- FOGSI (2020) — FOGSI Clinical Practice Guidelines: Antenatal Care in Low-Risk Pregnancies
Learn more about this test
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