Every living human has blood, and we know that blood comes in different types. There are four main blood group types A, B, AB and O and some of us have another factor called Rh D. If you are one of the people who have the RhD factor, you have a positive blood group (such as O positive), but if you don’t have the RhD factor, your blood is a negative blood type (for example A negative).
Your baby’s blood type is inherited from you and your baby’s father so your baby may have a different blood type to you. This is usually not a problem for you or your baby but issues may occur when a mother has a RhD negative blood group and her baby is RhD positive.
Women whose blood group is Rh-negative sometimes form Rh-antibodies when pregnant with a Rh-positive baby, in response to the baby's different red blood cell make-up. The mothers body sees the baby as a foreign invader and makes antibodies in response to the baby’s blood, in the same way it would in response to bacteria or a virus. This sensitisation is more likely to happen during birth, but occasionally occurs in late pregnancy. These antibodies generally don’t cause problems for the baby at the time but can cause anaemia, and sometimes death, for a Rh-positive baby in any pregnancies afterwards. Giving the mother anti-D after the first birth is known to reduce this problem.
In Australia, the Anti D injection is offered to pregnant RhD Negative women at around 28 weeks and 36 weeks gestation. It is important to understand that this is an offer, and not mandatory and if you want to refuse this, you are within your rights to do so. It is also reasonable to ask questions until you understand why you are offered the anti-D and make a decision based on that information.
Anti-D immunoglobulin is derived from human blood plasma and is administered by injection, which may not be acceptable to all women.
As with any medication or blood product, some women can have a reaction to the anti-D, which can include a rash or flu-like symptoms and, although the donated blood plasma will be screened carefully, there is still a small chance that an infection could be transferred through the injection of Anti-D.
You will be offered Anti D, whether or not you plan on having another baby and you may want to think about whether you will accept the anti D injection if you have decided not to have any more babies, or if the father of your baby is known to have an RhD negative blood type.
If you decide you will not have the anti D because you are not planning to have another baby, it is important to ensure you are using reliable contraception. Some reports have found that between 25% and 50% of all pregnancies may be unplanned, and the risks to an unplanned baby, if the mother is sensitised to a positive blood group baby can be severe.
As always, speak to your midwife or doctor if you have any questions and remember that no one decision is the right one for everyone.