Everyone has a blood group, or a blood type. The groups are O, A, B and AB. As well as this, a person may or may not contain a protein in their blood called Rhesus factor. A person who has the Rhesus factor is called "Rhesus positive" and a person who does not have this factor is called "Rhesus negative". So people may be (for example) O positive, A negative, AB positive and so on. About 85% people are Rhesus positive. That is, they contain the Rhesus factor in their blood, so their blood group would be one of the positive ones. The other 15% of people do not have this factor in their blood. A pregnant woman's blood group and Rhesus factor are determined by a blood test as part of the tests that are done when a woman first discovers she is pregnant.
If a pregnant woman has a negative blood group and her partner has a positive blood group, there is a chance that the baby will also have a positive blood group. Should any of the baby's blood get into the mother's system, her body will make antibodies to the baby's Rhesus factor. This doesn't cause any problems in the current pregnancy, but the next time the woman falls pregnant, the antibodies can affect the baby. The baby can be born prematurely, miscarriage is more likely, the baby may be born anaemic and the baby is more likely to experience jaundice.
Fortunately, there is something that can be done to prevent this all from happening!
Women who are a negative blood group will be offered two injections of Anti-D in pregnancy. This prevents any antibodies from forming. After the baby is born, the baby's blood group will be determined from blood that is in the cord, and if the baby's blood group is found to be positive, the mother will be given another dose of Anti-D.
Melissa Maimann is an eligible midwife in private practice in Sydney. One of the first eligible midwives in Australia, Melissa offers a range of care options for women. Visit Melissa's website to learn more about her services.