If you found out at your booking appointment with your midwife that you’re rhesus negative, this is what it means...
Rhesus negative: what it means
You will be offered a test for your blood group (A, B, AB or O) at your initial booking in appointment (NHS, 2020). The blood test will also check for the RhD antigen and show whether you’re rhesus positive (RhD-positive) or rhesus negative (RhD-negative) (NICE, 2021).
Blood types are inherited from your parents. That means you might have inherited a copy of the RhD antigen from either or both of your parents. But you'll only have rhesus negative blood if you didn’t inherit any copies of the RhD antigen from your parents (NHS, 2021).
A rhesus negative woman can only have a rhesus positive baby if their partner’s blood is rhesus positive. If the father has two copies of the RhD antigen, then all of his children will have rhesus positive blood. If the father has one copy of the RhD antigen, there is a 50% chance of his child being rhesus positive (NHS, 2021).
About 15% of the UK population are rhesus negative (NHS, 2021). Blood tests are offered to pregnant women to be able to diagnose or prevent rhesus disease.
What is rhesus disease?
Rhesus disease, or haemolytic disease of the foetus and newborn (HDFN), can lead to a baby having anaemia and jaundice. This is because antibodies in a pregnant women’s blood attack her baby’s blood cells (NHS, 2021).
What causes rhesus disease?
Rhesus disease is rare and treatable. It can appear when the following three occur together:
- a mother has a rhesus negative blood type
- their baby has a rhesus positive blood type
- the mother has been exposed to rhesus positive blood previously and has developed an immune response to it (this is called sensitisation).
Rhesus negative and pregnant
If your blood is rhesus negative, your blood sample will be checked for anti-D antibodies (NHS, 2021). If you do not have these antibodies, you will be offered injections of anti-D immunoglobin throughout your pregnancy. This will reduce the likelihood of you developing an immune response to your baby’s rhesus positive blood during pregnancy (Qureshi et al, 2014; NHS, 2021).
Being rhesus negative is unlikely to cause a problem in a first pregnancy. Even without the anti-D immunoglobin, it is unlikely that antibodies would be produced quickly enough to harm the baby (NHS, 2021). It can become an issue if the pregnancy or birth causes the mother to become sensitised to their baby's rhesus positive blood and create antibodies. This can affect future pregnancies with rhesus positive babies.
At around 12 weeks of pregnancy, it might be possible to determine your baby's blood group via a blood test taken from you. If your baby is rhesus negative, then they are at no risk of rhesus disease and they will not need extra monitoring or treatment (NHS, 2021). Sometimes, a blood test from the father will also be able to rule out rhesus positive blood in the baby (NHS, 2021).
If a baby is at risk of developing rhesus disease, extra monitoring during pregnancy will be offered. At birth a baby’s blood will be tested to see whether they have any anti-D antibodies in their blood (NHS, 2021).
Rhesus disease treatment
Rhesus disease is uncommon because usually it can be prevented with injections of anti-D immunoglobin (Qureshi et al, 2014; McBain et al, 2015; NHS, 2021). Around half of all cases of rhesus disease are minor and may need little treatment, with the baby simply being monitored regularly during pregnancy (NHS, 2021).
Rarely, the baby may need a blood transfusion while they’re in the womb. Others may be born early so they can have treatments. These treatments might include phototherapy (light therapy), sometimes intravenous antibodies from healthy donors and rarely a blood transfusion (NHS, 2021).
When is anti-D given?
If you’re rhesus negative and your partner is rhesus positive, you might be offered a couple of extra midwife appointments for your anti-D injections. NICE recommends routine anti-D injections for all pregnant RhD-negative women just in case sensitisation occurs (NICE, 2021).
Anti-D may also be offered after anything happens that might sensitise you to the RhD antigen. For example, a bleed or bump to the abdomen such as a fall or a car accident, or an invasive medical procedure (NICE, 2021).
As with all medicines, it is your choice whether or not to take it. Some people may want to consider that Anti-D is a blood product (NICE, 2022).
After your baby has been born, their blood will be checked to see whether it is RhD-positive. If it is, and you aren’t immune, you’ll be offered another anti-D injection (NHS, 2021).
This page was last reviewed in March 2022.
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McBain RD, Crowther CA, Middleton P. (2015) Anti-D administration in pregnancy for preventing Rhesus alloimmunisation. Cochrane Database Syst Rev. (9):CD000020. Available at: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD000020.pub3… [Accessed 1st March 2022]
NHS. (2020) Blood groups. Available at: https://www.nhs.uk/conditions/blood-groups/ [Accessed 1st March 2022]
NHS. (2021) Rhesus disease. Available at: https://www.nhs.uk/conditions/rhesus-disease/ [Accessed 1st March 2022]
NICE. (2021) Antenatal care for uncomplicated pregnancies. Available at: https://www.nice.org.uk/guidance/cg62 [Accessed 1st March 2022]
NICE. (2022) Anti-D (RH0) immunoglobulin. Available at: https://bnf.nice.org.uk/drug/anti-d-rh0-immunoglobulin.html [Accessed 1st March 2022]
Qureshi H, Massey E, Kirwan D, Davies T, Robson S, White J, et al. (2014) BCSH guideline for the use of anti-D immunoglobulin for the prevention of haemolytic disease of the fetus and newborn. Available at: https://doi.org/10.1111/tme.12091