Information for women with a Rhesus-Negative blood group
What does it mean to be Rhesus-Negative?
Human red blood cells carry many substances called antigens on their surfaces. Women who are Rhesus D positive have a substance called D-antigen on the surface of their red blood cells. Rhesus D negative women do not have any D-antigen present. Whether a person is Rhesus-Positive or Rhesus-Negative is determined by their genes. It is inherited from a parent.
A simple blood test can tell whether you are Rhesus-Positive or Rhesus-Negative. This test is part of your routine blood tests done during your pregnancy.
How does being Rhesus-Negative affect your pregnancy?
Problems can arise when a Rhesus-Negative mother carries a baby who is Rhesus-Positive. The baby may be Rhesus-Positive if the father is Rhesus-Positive.
During pregnancy and delivery, small amounts of your baby’s blood will cross into your blood stream. If your baby is Rhesus-Positive, your body will produce antibodies to fight the D-antigen that is present in the baby’s blood. This process is known as sensitisation. Rarely, sensitation can also occur after a previous miscarriage or ectopic pregnancy, or if you have received a transfusion of Rhesus-Positive blood by mistake (although this is extremely rare). After sensitisation, a memory of these antibodies is retained in the mother’s system.
Sensitisation usually does not affect your first pregnancy. If the next baby is also Rhesus-Positive, a large number of these antibodies can enter the baby’s blood stream and attack the baby’s red blood cells.
This can cause harm to the baby and result in a condition called haemolytic disease of the fetus and newborn, which results in anaemia, jaundice, severe brain damage, or even death of the baby.
How can I prevent these antibodies from causing problems in future pregnancies?
Anti-D immunoglobulin is an intramuscular injection which can prevent a Rhesus-Negative mother from producing antibodies against Rhesus-Positive blood cells.
When is Anti-D Immunoglobulin given?
Anti-D immunoglobulin is usually administered at around the 28th week of pregnancy to pregnant Rhesus-Negative women who are not already sensitised. Sensitisation is checked by a blood test that is done at the beginning of pregnancy and 1-2 weeks prior to administration of Anti-D immunoglobulin at the 28th week of pregnancy.
After childbirth, if your baby is found to be Rhesus-Positive, you will be given another Anti-D immunoglobulin injection, usually within 72 hours of the birth.
In addition, you are advised to have an Anti-D immunoglobulin injection following a potentially sensitising event, which is when there is a high risk of your blood and the blood of your baby becoming mixed. Anti-D immunoglobulin should be given as soon as possible and within 72 hours of a sensitising event. Examples of sensitising events include:
When do I NOT need to have Anti-D immunoglobulin?
Your doctor should discuss with you the situations where Anti-D immunoglobulin injection would be neither necessary nor cost effective. Such situations might include those where a woman:
What are the risks of Anti-D immunoglobulin?
You may experience some localised soreness at the injection site. You may also experience fever, headache, or flu-like symptoms after the injection.
Very rarely, Anti-D immunoglobulin can cause an allergic reaction. Early warning signs include rashes, chest tightness, and wheezing. Please seek medical help immediately if you develop these symptoms.
