If you have a negative blood group (Rh negative), and your baby is Rh positive, some of the baby’s blood cells may cross over into your blood stream during the pregnancy or at labour. Your immune system may see the Rh (D) positive blood cells from your baby as a foreign invader and produce antibodies against them. When your antibodies crosses the placenta, it can attack your baby’s blood cells, causing a serious anaemia in your baby. As it takes time for your body to produce the antibodies, it usually does not cause an issue in your first pregnancy. However, it can have serious effects in your next pregnancy. This condition is also known as Rhesus isoimmunization. Some babies might not survive the pregnancy, and some might require a blood transfusion while still in your womb.
Why is Anti-D given?
An Anti-D injection neutralises the Rh (D) positive blood cells from your baby before your body has a chance to make antibodies against them. Prior to the availability of Anti-D, fetal death from Rh isoimmunization were as high as 46/100,000 and it has now decreased to less than 1.6/100,000.
You can be assured that Rh isoimmunization is uncommon in Australia. From your initial pregnancy bloods, we would know if you are Rh (D) negative, and an Anti-D injection would be recommended.
When is Anti-D given?
It is usually given when you are 28 weeks and 34 weeks pregnant, if you are Rh (D) negative. There are other occasions when additional Anti-D might be recommended due to increased risk of baby’s blood crossing over to yours. The below conditions may be when an extra dose is recommended, and ideally within the 72 hours of it happening.
· Vaginal bleeding or spotting in pregnancy.
· Miscarriage
· If undergoing an amniocentesis or CVS sampling.
· Any physical accidents and mishaps i.e. a fall or a car accident
Upon the delivery of your baby, a blood sample will be collected from your baby’s cord blood and be sent for testing. If your baby is Rh (D) positive, you will receive another Anti-D injection. If your baby’s blood is Rh (D) negative, there is no need for an Anti-D.
For further information, a comprehensive article by Australian Red Cross, endorsed by RANZCOG (Royal Australian and New Zealand College of Obstetricians and Gynaecologists) is available for download below.
Dr Adeline Chan is a female obstetrician in Sydney, servicing the Western Sydney and Hills District region.
Download: You & Your Baby: Important Information for Rh (D) Negative Women Prevention of Haemolytic Disease of the Newborn