Sometimes during pregnancy there may be a mismatch between the mother and baby´s blood because of a protein found on red blood cells. This protein is called the Rhesus Factor. If we carry the Rhesus Factor we are Rhesus positive, if we do not we are Rhesus negative.
When both mother and baby are Rhesus negative there is no problem. If however, the mother is Rhesus negative and the baby Rhesus positive, future babies could be affected.
During pregnancy and at the time of birth, small amounts of the baby´s blood can cross through the placenta and into the mother´s blood stream. This is quite normal and happens in about 75% of pregnancies. As a result the mother will produce antibodies (blood proteins) to the baby´s blood. This process does not harm the baby being carried but could affect future pregnancies.
If the next baby is Rhesus positive too and its blood also passes into the mother´s blood stream, the levels of antibody will rise. These antibodies then return across the placenta where they destroy the baby´s blood cells. When this happens babies are said to have Haemolytic Disease of the Newborn or HDN.
A baby with HDN may suffer from several conditions ranging from mild anaemia and jaundice to brain damage and, in more serious cases, may even die.
HDN may be prevented very simply by an injection of Anti-D (Rho ) Immunoglobulin or Anti-D.
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