If you are Rhesus D negative (RhD negative), you will be offered an injection called anti-D immunoglobulin during pregnancy and after your baby is born. The purpose is to protect any future babies you may have from a condition called Haemolytic Disease of the Newborn (HDN).
This page explains what RhD means, what anti-D is, when it’s given, and what to expect.
Your blood is classified by two main systems: the ABO system (A, B, AB, O) and the Rhesus system, which includes the RhD antigen.
Most of the time, your RhD status makes no difference to your daily life. It becomes important if you are RhD negative and become pregnant with a baby who is RhD positive (which can happen if the baby’s father is RhD positive).
If small amounts of the baby’s RhD-positive blood enter your circulation, your immune system can produce antibodies against RhD. This is called sensitisation. It does not usually affect the current pregnancy, but in a future pregnancy with an RhD-positive baby, those antibodies can cross the placenta and attack the baby’s red blood cells, causing Haemolytic Disease of the Newborn (HDN).
HDN can be mild, causing only laboratory changes, or it can be severe, causing serious anaemia, jaundice, brain damage, or stillbirth.
Prophylaxis is the word for a medicine given to prevent something happening.
Anti-D prophylaxis means giving anti-D immunoglobulin to an RhD-negative woman to prevent her producing antibodies against RhD-positive blood cells, and so to prevent HDN in any future baby.
Anti-D immunoglobulin is made from a part of the blood called plasma, collected from screened donors. Production is very strictly controlled to ensure the chance of a known virus being passed from the donor is extremely low (estimated at 1 in 10,000 billion doses).
Each year in Ireland, around 5,000 RhD-positive babies are born to RhD-negative women. Anti-D prophylaxis has dramatically reduced the number of babies affected by HDN. Despite this, around 50 babies a year in Ireland still develop HDN and need close monitoring; 2 to 5 babies die each year as a result. The aim of giving anti-D is to prevent these outcomes.
When: Usually at week 28 of pregnancy (sometimes given as one dose at 28 weeks, or as two doses at 28 and 34 weeks).
Given by injection to RhD-negative women who have not already been “sensitised.” The aim is to cover the second half of pregnancy, when small amounts of fetal blood can cross the placenta.
When: After any event that can cause fetal blood to enter your circulation.
A targeted dose is given if you have a bleed in pregnancy, a fall or abdominal injury, amniocentesis or chorionic villus sampling, an external cephalic version, a miscarriage or termination. Tell your team early so the right dose can be given within 72 hours.
When: After your baby is born, within 72 hours of delivery.
After birth, a blood sample is taken from your baby’s umbilical cord to determine their blood group. If your baby is RhD positive, you are offered a post-birth dose of anti-D to prevent sensitisation from any blood transfer that occurred during the birth itself. If your baby is RhD negative, no post-birth dose is needed.
Anti-D is given as a single injection, usually into the muscle of your upper arm or buttock. It takes a few seconds.
You will be asked to read a patient information leaflet and to consent to receiving anti-D. Take the leaflet home, and ask your midwife or doctor anything you are unsure about.
It is much better to ring and find out you didn’t need a dose than to not ring and discover later that you did.
In some situations, routine antenatal anti-D may not be required. Your team will discuss these with you so you can make an informed choice. They include if:
These decisions are personal, and the only person who can decide is you, with full information. The benefits and risks of anti-D will be discussed clearly so that you can choose what is right for you.
Yes. Anti-D has been in routine use for over 50 years and is one of the most thoroughly studied interventions in obstetrics. The production process screens out all known viruses; the residual risk is extremely small.
Anti-D is a blood product (an immunoglobulin from donor plasma). Some women prefer not to receive blood-derived products on religious or personal grounds. We respect your decision. Your team will discuss the implications for you and any future pregnancies, so you can decide with full information.
Tell your midwife or GP as soon as possible. It can usually still be given. The protection is best when given on schedule, but a late dose is better than none.
No. If your baby is RhD negative, there is no risk of you producing antibodies against RhD, and a post-birth dose is not needed.
Yes. Anti-D does not affect breastfeeding.
You will be offered anti-D in each future pregnancy as if it were the first time. Your antibody status will be checked at the start of each pregnancy.
The Clinical Practice Guideline on the Use of Anti-D Immunoglobulin is available on the HSE website. Your midwife and GP can also answer specific questions.
